Magnetic resonance imaging apparatus

ABSTRACT

MRI apparatus includes an RF coil device, a first radio communication unit, a second radio communication unit, an image reconstruction unit and a judging unit. The RF coil device detects an MR signal, and includes a data saving unit for storing the MR signal. The first radio communication unit wirelessly transmits the MR signal detected by the RF coil device, and the second radio communication unit receives the MR signal from the first radio communication unit. The image reconstruction unit reconstructs image data using the MR signal. The judging unit judges existence of a transmission error in radio communication between the first and second radio communication units. If the transmission error is present, the first radio communication unit wirelessly transmit the MR signal stored in the data saving unit to the second radio communication unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of No. PCT/JP2013/74224,filed on Sep. 9, 2013, and the PCT application is based upon and claimsthe benefit of priority from Japanese Patent Application No.2012-200768, filed on Sep. 12, 2012, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments described herein relate generally to a magnetic resonanceimaging apparatus.

2. Description of the Related Art

MRI is an imaging method which magnetically excites nuclear spin of anobject (a patient) set in a static magnetic field with an RF pulsehaving the Larmor frequency and reconstructs an image on the basis of MRsignals generated due to the excitation. The aforementioned MRI meansmagnetic resonance imaging, the RF pulse means a radio frequency pulse,and the MR signal means a nuclear magnetic resonance signal.

Here, an RF (Radio Frequency) coil device is a device which transmits anRF pulse to nuclear spin inside an object by, for example, supplying acoil with an RF pulse electric current and detects generated MR signals.

Some of RF coil devices are built-in type included in an MRI apparatusand other RF coil devices are recognized by a control unit of the MRIapparatus by being connected to a connection port of the MRI apparatussuch as local RF coil devices, for example.

In MRI, multi-channel structure is promoted in acquisition system of MRsignals. The above “channel” means each pathway of a plurality of MRsignals outputted from each coil element and inputted to an RF receiverof an MRI apparatus. Although the number of channels is set to equal toor smaller than the input reception number of the RF receiver, a largenumber of RF coil devices can be connected to an MRI apparatus.

If the number of cables between an RF coil device and an MRI apparatusincreases due to promotion of the aforementioned multichannel structure,it is inconvenient because hard-wiring becomes complicated.

Therefore, it is desired to unwire transmission and reception of signalsbetween an RF coil device and an MRI apparatus. However, radiocommunication by an analogue signal has not been achieved, because thereare various restrictions such as degradation of dynamic range.

More specifically, in order to suppress influence on receivingsensitivity to weak MR signals emitted from an object, it is impossiblein an MRI apparatus to enlarge the output of electromagnetic waves usedfor radio communication between an RF coil device and an MRI apparatus.If it is impossible to enlarge the radio output power, dynamic rangedegrades due to signal loss caused when transmitted signals travelspace. Then, in Japanese Patent Application Laid-open (KOKAI)Publication No. 2010-29664, “digital radio communication method in whichMR signals are digitized and then transmitted wirelessly” is proposed.

Although the problem of restriction of dynamic range can be solved bywirelessly transmitting MR signals after digitalization, this method hasthe following problems.

Firstly, regulation of radio communication is different from country tocountry, and the same transmission frequency or the same transmissionpower cannot be necessarily used in other countries.

Secondly, if MR signals are wirelessly transmitted from an RF coildevice to an MRI apparatus, the transmitted radiowaves are reflected offsurrounding areas and this degrades own data of radio communication.

Therefore, a novel technology to wirelessly transmit digitized MRsignals from an RF coil device to an MRI apparatus satisfactorily hasbeen desired in MRI.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram showing the general structure of the MRIapparatus of the first embodiment;

FIG. 2 is a schematic diagram showing an example of structure of an RFcoil device and arrangement of control side radio communication devices;

FIG. 3 is a schematic cross-sectional diagram showing an example of amethod of fixing the coil side radio communication device to the controlside radio communication device;

FIG. 4 is a schematic block diagram showing the functions of therespective units relevant to transmission of MR signals detected by coilelements of the RF coil device;

FIG. 5 is an explanatory diagram showing the data type of MR signalsstored in memory elements;

FIG. 6 is a schematic circuit diagram showing an example of judgingwhether or not it is in execution of a scan in the case of an activetrap circuit;

FIG. 7 is a schematic circuit diagram showing an example of judgingwhether or not it is in execution of a scan in the case of a passivetrap circuit;

FIG. 8 is an explanatory diagram showing an example of judging the starttiming of a scan on the basis of the transmission timing of anexcitation RF pulse;

FIG. 9 is a schematic diagram showing an example of a guide display inmethods of collecting data manually;

FIG. 10 is a schematic oblique drawing showing an example of arrangementof a data collecting unit;

FIG. 11 is a schematic diagram showing an example of a warning display,when an RF coil device for the lumber part is used in addition to an RFcoil device for the chest part and the radio communication status is notnormal;

FIG. 12 is a flowchart illustrating an example of flow of the imagingoperation performed by the MRI apparatus of the first embodiment;

FIG. 13 is a block diagram showing general structure of the MRIapparatus of the second embodiment;

FIG. 14 is a flowchart illustrating an example of flow of the imagingoperation performed by the MRI apparatus of the second embodiment;

FIG. 15 is a block diagram showing an example of connecting the RF coildevice for the lumber part and the RF coil device for the chest part inparallel to each of the control side radio communication devices; and

FIG. 16 is a block diagram showing an example of mutually connecting theRF coil device for the lumber part, the RF coil device for the chestpart, and one control side radio communication device in series.

DETAILED DESCRIPTION

In the following embodiments, “a first radio communication unit and asecond radio communication unit both of which are capable of radiocommunication via an induced electric field” are disposed on an RF coildevice side and a control side of an MRI apparatus respectively. In thiscase, the first radio communication unit is detachably fixed to thesecond radio communication unit within near distance, for example, anddigitized MR signals are wirelessly transmitted from the first radiocommunication unit to the second radio communication unit via an inducedelectric field.

The aforementioned assignment of wirelessly transmitting digitized MRsignals from an RF coil device to a control side of an MRI apparatussatisfactorily can be achieved by the above novel technology.

In the above configuration, there is a possibility of occurringcommunication failure due to reasons as follows. For example, the RFcoil device set on an object may be moved due to large movement of theobject during imaging, and this stirs the first radio communication unitconnected to the RF coil device with a cable. In such a case, there is apossibility that a part of data of MR signals to be normally andwirelessly transmitted becomes a transmission error on the receivingside.

The above transmission error means, for example, transmission ofincorrect data, lack of data and so on. Thus, “a configuration in whicha transmission error is compensated even in the case of a communicationdisturbance” is preferable. Then, in the following embodiments, it is afurther assignment to compensate a transmission error of data of MRsignals caused by communication disturbance.

For example, according to one embodiment, an MRI apparatus includes anRF coil device, a first radio communication unit, a second radiocommunication unit, an image reconstruction unit and a judging unit.

The RF coil device detects an MR signal emitted from an object anddigitizes the MR signal. In addition, the RF coil device includes a datasaving unit that stores the detected MR signal.

The first radio communication unit wirelessly transmits the digitized MRsignals.

The second radio communication unit receives the MR signal wirelesslytransmitted from the first radio communication unit.

The image reconstruction unit reconstructs image data on the basis ofthe MR signal received by the second radio communication unit.

The judging unit judges whether or not a transmission error of data ofthe MR signal is present in radio communication between the first radiocommunication unit and the second radio communication unit. When thejudging unit judges that the transmission error is present, the firstradio communication unit wirelessly transmits the MR signal stored inthe data saving unit to the second radio communication unit.

Examples of embodiments of magnetic resonance imaging apparatuses andmagnetic resonance imaging methods to which the aforementionedconfiguration are applied will be concretely described with reference tothe accompanying drawings as follows.

Note that the same reference numbers are given for identical componentsin each figure, and overlapping explanation is abbreviated.

The First Embodiment

FIG. 1 is a block diagram showing an example of the general structure ofthe MRI apparatus 20A according to the first embodiment. As shown inFIG. 1, the MRI apparatus 20A includes a gantry 21, a bed 32 and a table34. The table 34 is movably disposed on the bed 32 so as to be supportedby the bed 32. In addition, in the gantry 21 which is cylinder-shaped asan example, the MRI apparatus 20A includes a static magnetic fieldmagnet 22, a shim coil 24, a gradient magnetic field coil 26 and atransmission RF coil 28. The gantry 21 corresponds to the partsindicated as bold line frames in FIG. 1.

An object P is set on the table 34. The static magnetic field magnet 22and the shim coil 24 are, for example, cylinder-shaped. Inside thestatic magnetic field magnet 22, the shim coil 24 is arranged so as tobecome coaxial with the static magnetic field magnet 22.

As an example here, an apparatus coordinate system, whose X axis, Y axisand Z axis are perpendicular to each other, is defined as follows.

Firstly, it is assumed that the static magnetic field magnet 22 and theshim coil 24 are arranged in such a manner that their axis directionaccords with the vertical direction. And the direction of the axis ofthe static magnetic field magnet 22 and the shim coil 24 is defined asthe Z axis direction. In addition, it is assumed that the verticaldirection is the same as the Y axis direction. Moreover, it is assumedthat the table 34 is disposed in such a position that the direction of“the normal line of the loading plane thereof” is the same as the Y axisdirection.

The MRI apparatus 20A includes, on its control side, a static magneticfield power supply 40, a shim coil power supply 42, a gradient magneticfield power supply 44, an RF transmitter 46, an RF receiver 48, a tabledriving device 50, a system control unit 52, a system bus 54, an imagereconstruction unit 56, an image database 58, an image processing unit60, an input device 62, a display device 64 and a storage device 66.Incidentally, the table driving device 50 is arranged inside the bed 32.

The static magnetic field magnet 22 forms a static magnetic field in animaging space by using an electric current supplied from the staticmagnetic field power supply 40. The aforementioned “imaging space”means, for example, a space in the gantry 21 in which the object P isplaced and to which a static magnetic field is applied.

The static magnetic field magnet 22 includes a superconductivity coil inmany cases. The static magnetic field magnet 22 gets the electriccurrent from the static magnetic field power supply 40 at excitation.However, once excitation has been made, the static magnetic field magnet22 is usually isolated from the static magnetic field power supply 40.The static magnetic field magnet 22 may include a permanent magnet whichmakes the static magnetic field power supply 40 unnecessary.

The shim coil 24 is electrically connected to the shim coil power supply42 and uniforms the static magnetic field with the electric currentsupplied from the shim coil power supply 42.

The gradient magnetic field coil 26 is, for example, arranged in theform of a cylinder inside the static magnetic field magnet 22. Thegradient magnetic field coil 26 generates a gradient magnetic field Gxin the X axis direction, a gradient magnetic field Gy in the Y axisdirection and a gradient magnetic field Gz in the Z axis direction inthe imaging region, by using electric currents supplied from thegradient magnetic field power supply 44.

That is, directions of “a gradient magnetic field Gss in a sliceselection direction”, “a gradient magnetic field Gpe in a phase encodingdirection” and “a gradient magnetic field Gro in a readout (frequencyencoding) direction” can be arbitrarily set as logical axes, bycombining the gradient magnetic fields Gx, Gy and Gz in the three axesof the apparatus coordinate system.

Note that, the above “imaging region” means, for example, a region setas a part of the imaging space and is a range of acquisition of MRsignals used to generate “one image” or “one set of image”. Here, “oneset of images” means, for example, a plurality of images when MR signalsof the plurality of images are acquired in a lump in one pulse sequencesuch as multi-slice imaging. The imaging region is definedthree-dimensionally in an apparatus coordinate system, for example.

The RF transmitter 46 generates RF pulses in accordance with controlinformation provided from the system control unit 52, and transmits thegenerated RF pulses to the transmission RF coil 28. The transmission RFcoil 28 transmits RF pulses given from the RF transmitter 46 to theobject P. The transmission RF coil 28 also includes “a whole body coil(not shown) which is included in the gantry 21 and used for bothtransmission of RF pulses and detection of MR signals”.

The reception RF coil 29 is disposed inside the table 34. The receptionRF coil 29 detects MR signals generated due to excited nuclear spininside the object P by the RF pulse, and transmits the detected MRsignals to the RF receiver 48.

The RF coil device 100A is, for example, a wearable local RF coil devicefor detecting MR signals. Here, “the RF coil device 100A which is set onthe chest part and detects MR signals from the chest part” is shown, butthis is only an example. In the MRI apparatus 20A, various wearable RFcoil devices such as a shoulder RF coil device and a lumbar part RF coildevice 100α (see later-described FIG. 10) can be used for detection ofMR signals aside from the RF coil device 100A.

As an example here, each of these RF coil devices (100A, 100α) fordetecting MR signals are interpreted as a part of the MRI apparatus 20A.However, these RF coil devices may be interpreted as separatedcomponents from the MRI apparatus 20A.

The RF coil device 100A includes a cable 102, and is connected to thecoil side radio communication device 200A by the cable 102.

Inside the table 34, a plurality of control side radio communicationdevices 300 are arranged. The aforementioned radio communication ofdigitized MR signals is performed between one coil side radiocommunication device 200A and one of the control side radiocommunication devices 300.

However, in the case of setting a plurality of RF coil devices on theobject P as an example, the present embodiment is not limited to theabove aspect. In such a case, for example, radio communication of thedigitized MR signals is respectively performed between “each of theplurality of the coil side radio communication devices 200A respectivelycorresponding to the RF coil devices” and “each of the plurality of thecontrol side radio communication devices 300 respectively correspondingto the plurality of the coil side radio communication devices 200A”.

Thus, the coil side radio communication device 200A of the MRI apparatus20A is an example of the first radio communication unit described in theclaims, and the control side radio communication devices 300 of the MRIapparatus 20A is an example of the second radio communication unitdescribed in the claims. Operation of the radio communication will bedescribed later.

Note that, though only two of the control side radio communicationdevices 300 are shown in FIG. 1 to avoid complication, the number of thecontrol side radio communication devices 300 may be one, three or morethan three.

However, configuration of including many of the separately arrangedcontrol side radio communication devices 300 is more preferable thanconfiguration of including only one control side radio communicationdevice 300. This is because the former has more choices to closely fixthe coil side radio communication device 200A to the control side radiocommunication device 300.

In other words, if there are more choices of a fixing position, the coilside radio communication device 200A can be fixed on the nearest controlside radio communication device 300 thereto. If it is fixed in such amanner, the cable 102 between the RF coil device 100A and the coil sideradio communication device 200A can be shortened.

Note that, the aforementioned “closely fix” means, for example, to fixmutually immovably within a range (distance) of being mutuallyelectromagnetically coupled so as to be capable of radio communicationvia an induced electric field.

In addition, as an example in the present embodiment, transmission of anRF pulse to the transmission RF coil 28 inside the MRI apparatus 20A andtransmission of MR signals detected from the object P are performedunder wire transmission except the pathway between the coil side radiocommunication device(s) 200A and the control side radio communicationdevice(s) 300.

The RF receiver 48 generates complex number data of digitized MR signals(hereinafter, referred to as raw data of MR signals) by performingpredetermined signal processing. The RF receiver 48 inputs the generatedraw data of MR signals to the image reconstruction unit 56.

The system control unit 52 performs system control of the entirety ofthe MRI apparatus 20A in imaging operation and an image display afterthe imaging operation via interconnection lines such as the system bus54.

For the sake of achieving the above control, the system control unit 52stores control information needed in order to make the gradient magneticfield power supply 44, the RF transmitter 46 and the RF receiver 48drive. The aforementioned “control information” includes, for example,sequence information describing operation control information such asintensity, application period and application timing of the pulseelectric currents which should be applied to the gradient magnetic fieldpower supply 44.

The system control unit 52 generates the gradient magnetic fields Gx, Gyand Gz and RF pulses by driving the gradient magnetic field power supply44, the RF transmitter 46 and the RF receiver 48 in accordance with apredetermined sequence stored.

In addition, the system control unit 52 can change the height of the bed32 so as to move up and down the table 34 in the Y axis direction bycontrolling the table driving device 50 (when the table 34 is at apredetermined position outside the gantry 21). In addition, the systemcontrol unit 52 makes the table 34 move into and out of the imagingspace in the gantry 21 in the Z axis direction by controlling the tabledriving device 50. The system control unit 52 locates the imaging partof the object P near to the center of the magnetic field in the imagingspace by controlling the position of the table 34 in the above manner.

In addition, the system control unit 52 functions as an imagingcondition setting unit. That is, the system control unit 52 sets theimaging conditions of the main scan on the basis of some of the imagingconditions and information inputted to the input device 62 by a user.For the sake of achieving this, the system control unit 52 makes thedisplay device 64 display screen information for setting the imagingconditions.

The input device 62 provides a user with a function to set imagingconditions and image processing conditions.

The aforementioned term “imaging condition” refers to under whatcondition an RF pulse or the like is transmitted in what type of pulsesequence, or under what condition MR signals are acquired from theobject P, for example. As a parameter of the “imaging conditions”, forexample, there are “the imaging region as positional information in theimaging space”, an imaging part, the type of the pulse sequence such asparallel imaging, the type of RF coil devices used for imaging, thenumber of slices, an interval between respective slices.

The above “imaging part” means a region of the object P to be imaged asan imaging region, such as a head, a chest and an abdomen.

The aforementioned “main scan” is a scan for imaging an intendeddiagnosis image such as a proton density weighted image, and it does notinclude a scan for acquiring MR signals for a scout image or acalibration scan.

A scan is an operation of acquiring MR signals, and it does not includeimage reconstruction processing.

The calibration scan is, for example, a scan for determining“unconfirmed elements of imaging conditions”, “conditions and data usedfor image reconstruction processing” and so on, and it is performedseparately from the main scan.

The after-mentioned “prescan” is a calibration scan which is performedbefore the main scan.

The image reconstruction unit 56 converts the raw data of MR signalsinputted from the RF receiver 48 into, for example, matrix data on thebasis of a phase encode step number and a frequency encode step number,and stores the converted data as k-space data. The k-space means afrequency space (Fourier space). The image reconstruction unit 56generates image data of the object P by performing image reconstructionprocessing including such as two-dimensional Fourier transformation onthe k-space data. The image reconstruction unit 56 stores the generatedimage data in the image database 58.

The image processing unit 60 takes in the image data from the imagedatabase 58, performs predetermined image processing on them, and storesthe image data after the image processing in the storage device 66 asdisplay image data.

The storage device 66 stores the display image data after adding“accompanying information such as the imaging conditions used forgenerating the display image data and information of the object P(patient information)” to the display image data.

The display device 64 displays a screen for setting imaging conditionsof the main scan and images indicated by generated image data undercontrol of the system control unit 52.

FIG. 2 is a schematic diagram showing an example of the structure of theRF coil device 100A and an example of arrangement of the control sideradio communication devices 300. As shown in FIG. 2, the RF coil device100A includes the cable 102 and a cover member 104. The cover member 104is made of a flexible material and is capable of deformation such asfolding. As such a deformable (flexible) material, for example, aflexible circuit board (Flexible Printed Circuit FPC) described inJapanese Patent Application Laid-open (KOKAI) Publication No.2007-229004 can be used.

Inside the cover member 104, a plurality of coil elements (surfacecoils) 106 a, 106 b, 106 d, 106 d, 106 e and 106 f functioning asantennas which respectively detect MR signals from the object P aredisposed. Although six coil elements 106 a to 106 f are shown in FIG. 2as an example here, the number or shape of the coil elements are notlimited to the shown number or shape.

In addition, inside the cover member 104, a selection control unit 108which controls the operation of the RF coil device 100A such asselection of the coil elements (106 a to 106 f) for detection isdisposed. Although there are other components such as A/D (analog todigital) converter 140 a inside the cover member 104, their details willbe described later with FIG. 4.

As an example here, the coil side radio communication device 200A andthe RF coil device 100A are assumed to be mutually separate components,but this is only an example of interpretation. The coil side radiocommunication device 200A may be interpreted as a part of the RF coildevice 100A.

The cable 102 is connected to the coil side radio communication device200A of the MRI apparatus 20A on its one end, and is connected to theselection control circuit 108 and so on inside the cover member 104 onits other end.

In addition, inside the cover member 104 of the RF coil device 100A,components such as preamplifiers PMPa to PMPf (see after-mentioned FIG.4) for amplifying the MR signals detected by the coil elements 106 a to106 f and bandpass filters for filtering may be disposed.

As an example here, eight of the control side radio communicationdevices 300 are arranged immediately beneath the surface of the table 34on which the object P is loaded (hereinafter, this surface is referredto as the top surface of the table 34).

The object P is, for example, loaded in the middle of the widthdirection (the X axis direction in FIG. 1) of the table 34. Thus, inthis example, on both end sides in the width direction of the table 34,four of the control side radio communication devices 300 arerespectively arranged along the longer direction of the table 34 (the Zaxis direction) in a row at intervals.

In addition, the chassis 302 (see after-described FIG. 3) of each of thecontrol side radio communication devices 300 is embedded immediatelybeneath the top surface of the table 34, and its fixing plates 321 (seeafter-described FIG. 3) are exposed out of the top surface of the table34. The coil side radio communication device 200A is detachably fixed tothe control side radio communication device 300 by being interdigitatedwith the fixing plates 321.

Thus, no matter which part of the object P an RF coil device is set on,the coil side radio communication device 200A can be closely fixed tothe nearest control side radio communication device 300. Although thepresent embodiment is an example of the RF coil device 100A for thechest part, this point applies to combination of an RF coil device foranother part and the coil side radio communication device 200A.Therefore, the length of the cable 102 can be shortened.

Note that, the number or arrangement position of the control side radiocommunication devices 300 is not limited to that of FIG. 2 (inside thetable 34). For example, the control side radio communication devices 300may be disposed and exposed on the table 34 or on the gantry 21.Alternatively, the control side radio communication devices 300 may bedisposed inside the gantry 21 or on the bed 32.

FIG. 3 is a schematic cross-sectional diagram showing an example of amethod of fixing the coil side radio communication device 200A to thecontrol side radio communication device 300.

As shown in the upper part of FIG. 3, for example, two bumps 221 areformed on the chassis 202 of the coil side radio communication device200A.

In order to facilitate insertion and detachment of the coil side radiocommunication device 200A, each bump 221 is shaped in such a manner thatits transverse section becomes a semicircle, for example. This isbecause smoothly chamfered surfaces of the bumps 221 make it easier toinsert the coil side radio communication device 200A than bumpy surfacesthereof, in general. The bumps 221 may be spherical, for example.Alternatively, the bumps 221 may be in the form of a bisected cylinderdivided along its axis direction.

As an example here, “the chassis 202 which includes the bump 221” isassumed to be made of undeformable nonmagnetic material. By forming itwith nonmagnetic material, influence on the radio communication via aninduced electric field can be unfailingly avoided.

The control side radio communication device 300 includes two fixingplates 321 fixed to ambilateral side surfaces of the chassis 302 by, forexample, adhesive bonding.

Both fixing plates 321 are approximately in the form of a flat plate,for example, and disposed so as to face each other. As shown in thelower part of FIG. 3, each of the fixing plates 321 is shaped in theform of interdigitating the coil side radio communication device 200A.That is, “dent parts 321 a in the form of interdigitating the bump 221”are respectively chamfered on “the mutually facing surfaces of the twofixing plates 321” at a position corresponding to each of the bumps 221(see the upper part of FIG. 3).

In addition, the end side (the side opposite to the chassis 302) of eachof the fixing plates 321 is chamfered aslant in order to ease insertionof the coil side radio communication device 200A. As to the fixingplates 321, it is preferable to form them with elastic material ofnonmagnetic body which can be curved to a degree shown in the middlepart of FIG. 3. As such material, for example, plastic and syntheticresin can be used. The reason for forming them with nonmagnetic materialis the same as before.

The control side radio communication device 300 is embedded behind thetop surface of the table 34 for the depth of interval D, for example(see the lower part of FIG. 3). The interval D is an interval capable ofthe radio communication via an induced electric field. On the topsurface of the table 34, “ditches into which the fixing plates 321 canbe inserted” are formed, and the fixing plates 321 stick out of the topsurface of the table 34 via these ditches.

In the above structure, the coil side radio communication device 200A isinserted into the side of the control side radio communication device300 from the state of the upper part of FIG. 3. At this insertiontiming, as shown in the middle part of FIG. 3, each of the fixing plates321 is bent in the direction of mutually separating. This is because themaximum width between both bumps 221 on the ambilateral side surfaces ofthe coil side radio communication device 200A is larger than the minimumwidth between both fixing plates 321.

Then, at the position where the basal plane of chassis 202 of the coilside radio communication device 200A has contact with the top surface ofthe table 34, both bumps 221 are respectively interdigitated with thedent parts 321 a, and each of the fixing plates 321 returns to theoriginal shape (shown in the upper part of FIG. 3 before insertion) byshape recovery force. Thereby, the coil side radio communication device200A is detachably fixed to the control side radio communication device300 on the table 34.

Here, the coil side radio communication device 200A includes antennas206 a to 206 d on its bottom aspect side (the side of the control sideradio communication devices 300 in the above fixed state). In addition,the control side radio communication device includes antennas 306 a to306 d on its top surface side (the side of the coil side radiocommunication device 200A in the above fixed state).

Each of the antennas 306 a to 306 d corresponds to each of the aboveantennas 206 a to 206 d so as to group into a pair (totally, fourpairs). Out of the antennas 206 a to 206 d and 306 a to 306 d, at leastthe antennas 206 a and 306 a are composed of, for example,later-described induced electric field combined couplers.

Under the state in which the coil side radio communication device 200Aand the control side radio communication device 300 are closely fixed toeach other as just described, the antennas 206 a to 206 d arerespectively disposed at positions where they face the antennas 306 a to306 d respectively. When imaging is finished, the coil side radiocommunication device 200A is taken out of the fixing plated 321 so as toseparate from the table 34.

Note that, the above interdigitation is only an example of methods offixing the coil side radio communication device 200A, and otherdetachable fixing methods may be alternatively used. For example, out ofthe male side and the female side of a hook-and-loop fastener, one sidemay be fixed to the top surface of the table 34 and the other side maybe fixed to the bottom surface of the coil side radio communicationdevice 200A. When the top surface of the control side radiocommunication device 300 is exposed out of the top surface of the table34, one side of the male side or the female side of a hook-and-loopfastener may be fixed to the top surface of the control side radiocommunication device 300.

The radio communication via an induced electric field is performed onthe pathway between the coil side radio communication device 200A andthe control side radio communication device 300A. An induced electricfield means an electric field caused by time change of magnetic fluxdensity. As short-distance radio communication via an induced electricfield, for example, “TransferJet (Trademark) which uses an inducedelectric field combined coupler as an antenna” can be used (see JapanesePatent Application Laid-open (KOKAI) Publication No. 2010-147922, forexample).

More specifically, the induced electric field combined coupler includesa coupling electrode, a resonance stub, a ground and so on (not shown).If an electric signal is inputted to the resonance stub of thetransmission side, electric charges are accumulated in the couplingelectrode, and “virtual electric charges equal to the electric chargesaccumulated in the coupling electrode” are generated in the ground.Thereby, a micro electrical dipole is composed by these electriccharges, and this micro electrical dipole functions as a transmissionside antenna. That is, data are transmitted to the receiving side via aninduced electric field of a longitudinal wave generated by the microelectrical dipole. Because a longitudinal wave vibrating in parallelwith the traveling direction is not influenced by the direction of anantenna, stable data transmission can be achieved.

However, if the receiving side is separated from the transmission sidebeyond limit, both sides are not electro-magnetically coupled and datatransmission cannot be performed. This is because induced electricfields formed by the induced electric field combined couplers rapidlyattenuate if the interval between both sides of the couplers becomesdistant.

Although the antennas 206 a to 206 d are discretely disposed and theantennas 306 a to 306 d are discretely disposed in order to distinguishrespective components in FIG. 3, interference between each of the fourradio communication pathways can be avoided without arranging themseparately.

More specifically, the four radio frequencies respectively used in thepathway of the antennas 206 a to 306, the pathway of the antennas 206 bto 306 b, the pathway of the antennas 206 c to 306 c and the pathway ofthe antennas 206 d to 306 d may be separated (their frequency values maybe widely set apart). As to the radio communication frequency, it ispreferable to avoid frequencies which are equal to numbers obtained bydividing “a center frequency of RF pulses transmitted to the object P”by a natural number, in each of the radio communication pathway.

It is preferable that installation positions of the control side radiocommunication devices 300 are not too deep from the top surface of thetable 34. If positions of the antennas 306 a to 306 d of each of thecontrol side radio communication devices 300A in the table 34 are toodeep, the interval D (see the bottom part of FIG. 3) between thetransmission side and the receiving side cannot be close enough toelectro-magnetically couple “the antennas 206 a to 206 d of thetransmission side” to “the antennas 306 a to 306 d of the receivingside”. In this case, the radio communication via an induced electricfield will be difficult to be achieved.

That is, it is preferable to dispose each of the control side radiocommunication devices 300 to such a position that “each control sideradio communication device 300 can be fixed to the coil side radiocommunication device 200A close enough to be electro-magneticallycoupled to the coil side radio communication device 200A”.

Note that, as long as “an electric dipole (antenna) of the coil sideradio communication device 200A side” is not directly contacted to “anelectric dipole (antenna) of the control side radio communication device300 side”, “the chassis covering the antennas of the coil side radiocommunication device 200A side” may be contacted to “the chassiscovering the antennas of the control side radio communication device 300side”. This is because it is enough if the interval D causing an inducedelectric field is kept between the antennas of the transmission side andthe antennas of the receiving side. Thus, the control side radiocommunication devices 300 may be exposed in such a manner that itssurface of the antennas side becomes in line with the top surface of thetable 34.

FIG. 4 is a schematic block diagram showing the functions of therespective units relevant to transmission of the MR signals detected bythe coil elements 106 a to 106 f of the RF coil device 100A. In thefollowing, each component will be explained from the top side of FIG. 4in order. That is, each component will be explained in the order of (1)the cover member 104 of the RF coil device 100A, (2) the coil side radiocommunication device 200A, (3) the control side radio communicationdevices 300 and (4) the control side of the MRI apparatus 20A.

Firstly, inside the cover member 104, the aforementioned selectioncontrol unit 108, the aforementioned plurality of coil elements 106 a to106 f, preamplifiers PMPa to PMPf, A/D converters 140 a to 140 f, a P/S(parallel/serial converter) 144, a rechargeable battery BA and a datasaving unit (data backup unit) 150 are disposed. Note that, in order toavoid complication, the coil elements 106 c to 106 f, the preamplifiersPMPc to PMPf and the A/D converters 140 c to 140 f are not shown in FIG.4.

The data saving unit 150 includes a storage control unit 152, anelectric field shield 156, and memory elements 160 a to 160 f inside theelectric field shield 156. Note that, in order to avoid complication,the memory elements 160 c to 160 f are not shown in FIG. 4. That is, inthis example, the number of the memory elements (160 a to 160 f) is thesame as the A/D converters (140 a to 140 f), the preamplifiers (PMPa toPMPf) and the coil elements (106 a to 106 f), respectively.

The A/D converters 140 a to 140 f respectively correspond to thepreamplifiers PMPa to PMPf, the preamplifiers PMPa to PMPf respectivelycorrespond to the coil elements 106 a to 106 f, and the memory elements160 a to 160 f respectively correspond to the A/D converters 140 a to140 f

The MR signals respectively detected by the coil elements 106 a to 106 fare respectively amplified by the corresponding preamplifiers PMPa toPMPf, then respectively digitized by the corresponding the A/Dconverters 140 a to 140 f, and then respectively stored in thecorresponding the memory elements 160 a to 160 f.

Each of the memory elements 160 a to 160 f backs up data of the MRsignals wirelessly transmitted via an induced electric field from thecoil side radio communication device 200A to the control side radiocommunication device 300. Therefore, if data of the MR signals are notnormally transmitted from the coil side radio communication device 200Ato the control side radio communication device 300, the stored data inthe memory elements 160 a to 160 f are used.

Thus, as the maximum number of the memory elements (160 a to 160 f), thesame number as the coil elements (106 a to 106 f) functioning asantennas is preferable. However, the number of the memory elements isnot limited to the above aspect, and it may be one, for example.Alternatively, the number of the memory elements may be half of the coilelements so that each of the memory elements backs up data of the MRsignals detected by two coil elements.

As the memory elements 160 a to 160 f, memory elements which arereadable and rewritable in a nonmagnetic manner are preferable in orderto avoid influence on transmission and reception of the MR signals.Thus, as the memory elements 160 a to 160 f, for example, semiconductormemory elements such as a flash memory and EEPROM (ElectronicallyErasable and Programmable Read Only Memory) can be used. As an examplein the present embodiment, it is assumed that flash memories are usedfor the memory elements 160 a to 160 f.

However, as to the memory elements 160 a to 160 f, they are not limitedto semiconductor memory elements. For example, an optical pickup devicemay be installed inside the data saving unit 150, so that storage anderasing of data are performed with laser onto a rewritable small-typeoptical disk. In this case, the electric field shield 156 may beomitted.

In addition, each of the memory elements 160 a to 160 f includes aconnection port such as USB (Universal Serial Bus), for example, anddetachably connectable with the data saving unit 150 via the connectionport. In addition, each of the memory elements 160 a to 160 f isdetachably connectable with the after-described data collecting unit 600(see FIG. 10).

The electric field shield 156 is, for example, a chassis formed by useof metal which is nonmagnetic material and has superior electricalconductivity. As such metal, for example, brass and copper can be used.Note that, the electric field shield 156 may be formed by coveringundeformable nonmagnetic body such as plastic with copper foil.

The storage control unit 152 controls operation of writing and erasingof data of the MR signals to each of the memory elements 160 a to 160 f.

Next, the coil side radio communication device 200A further includes adata transmitting unit 216, a reference signal receiving unit 218, an ID(Identification Information) transmitting unit 222, a gate signalreceiving unit 224 and a coil L2, in addition to the aforementionedantennas 206 a to 206 d.

In FIG. 4, the hard-wiring between the gate signal receiving unit 224and the selection control unit 108, the hard-wiring between the coil L2and the rechargeable battery BA, the hard-wiring between the referencesignal receiving unit 218 and each of the A/D converters 140 a to 140 f,and the hard-wiring between the P/S (parallel/serial converter) 144 andthe data transmitting unit 216 are included in the cable 102 (see FIG.2). In order to avoid complication, the cable 102 is not shown in FIG.4.

In addition, the power receiving unit 220 is composed of the coil L2inside the coil side radio communication device 200A and therechargeable battery BA inside the cover member 104.

Next, the control side radio communication devices 300 further includesa data receiving unit 316, a reference signal transmitting unit 318, apower supply unit 320, an ID (Identification Information) receiving unit322 and a gate signal transmitting unit 324, in addition to theaforementioned antennas 306 a to 306 d. In addition, the power supplyunit 320 includes a coil L1.

Next, the control system of the MRI apparatus 20A further includes afrequency upconversion unit 402, a pulse waveform generation unit 404, afixed frequency generation unit 406, a variable frequency generationunit 408, aside from the components shown in FIG. 1. In addition, the RFreceiver 48 includes a frequency downconversion unit 410 and a judgingunit 412.

As an example in the first embodiment, there are “a region where aninduced magnetic field for charging is generated” and “four radiocommunication pathways” between the coil side radio communication device200A and the control side radio communication device 300. In thefollowing, the above region and pathways will be explained in order.

Consider a case where the coil L2 of the power receiving unit 220 islocated in a position close enough to be electro-magnetically coupled tothe coil L1 of the power supply unit 320 (i.e. a case where the coilside radio communication device 200A is closely fixed to the controlside radio communication device 300 like the lower part of FIG. 3). Inthis case, the power supply unit 320 supplies a primary current to thecoil L1 so as to generate an induced magnetic field, and therebyelectromotive force is caused in the coil L2. By this electromotiveforce, a secondary current flows the coil L2, and thereby therechargeable battery BA is charged.

The power receiving unit 220 provides the electric power charged in theabove manner to each component of the coil side radio communicationdevice 200A and the RF coil device 100A via hard-wiring (not shown).

Here, as to the frequency of the primary current supplied to the coilL1, it is preferable to separate the frequency from each communicationfrequency used in the four radio communication pathways. This is so thatsignals in the four radio communication pathways between the antennas206 a to 206 d and the antennas 306 a to 306 d are not interfered by theabove primary current.

Note that, as a method of saving electric power of the RF coil device100A, instead of the power receiving unit 220 and the power supply unit320, another rechargeable battery may be embedded in the RF coil device100A and this rechargeable battery may be charged during unused span ofthe RF coil device 100A. Alternatively, “another rechargeable batterycharged during unused span of the RF coil device 100A” and “the abovepower receiving unit 220 and the power supply unit 320” may be used incombination.

Next, the four radio communication pathways will be explained. Althoughthe radio communication via an induced electric field is performed atleast in the pathway between the antennas 206 a and 306 a, it may beperformed in the pathway between the antennas 206 b and 306, or thepathway between the antennas 206 d and 306 d.

Firstly, in the pathway between the antennas 206 c and 306 c, theidentification information of the RF coil device 100A is transmittedfrom the coil side radio communication device 200A to the control sideradio communication device 300.

More specifically, for example, the above identification information ispreliminarily stored in the ID transmitting unit 222. However, theidentification information of the RF coil device 100A may be inputtedfrom the selection control unit 108 into the ID transmitting unit 222 ofthe coil side radio communication device 200A via the cable 102.

If the antenna 306 c of the ID receiving unit 322 gets close to theantenna 206 c of the ID transmitting unit 222, the ID transmitting unit222 operates on the basis of electric power wirelessly supplied from theID receiving unit 322. That is, the ID transmitting unit 222automatically transmits the identification information from the antenna206 c to the antenna 306 c as a digital signal. This radio communicationof the identification information may be performed in the same way asRFID (Radio Frequency Identification) typified by, for example, IC(Integrated Circuit) tag.

The ID receiving unit 322 inputs the identification information of theRF coil device 100A received by the antenna 306 c to the system controlunit 52. Thereby, the system control unit 52 recognizes information onwhich of various types of RF coil devices such as the chest part RF coildevice and the shoulder RF coil device is(are) currently connected.

Secondly, in the pathway between the antennas 306 d and 206 d, a gatesignal is continuously wirelessly transmitted from the gate signaltransmitting unit 324 of the control side radio communication device 300to the gate signal receiving unit 224 of the coil side radiocommunication device 200A during imaging.

More specifically, as a switch changing on/off state of each of the coilelement 106 a to 106 f of the RF coil device 100A, for example, anactive trap circuit 170 including a PIN diode (p-intrinsic-n Diode) andso on are used (see after-described FIG. 6). The gate signal is, forexample, a signal stipulating the switching timing of impedance of thetrap circuit (a control signal of the above switch).

Note that, as an alternative configuration, a trigger signal may betransmitted from the gate signal transmitting unit 324 to the gatesignal receiving unit 224 and the gate signal is generated inside thegate signal receiving unit 224 on the basis of the trigger signal.

While RF pulses are transmitted to the object P, the gate signalinputted to the RF coil device 100A via the gate signal transmittingunit 324, the antenna 306 d, the antenna 206 d and the gate signalreceiving unit 224 is generally set to on-level. During the on-levelspan of the gate signal, the above switch becomes off-state so as todisconnect the loop of each of the coil elements 106 a to 106 f andthereby each of the coil elements 106 a to 106 f cannot detect MRsignals.

Except the span during which RF pulses are transmitted to the object P,the gate signal adjusted to off-level is wirelessly transmitted. Whilethe gate signal is off-level, the above switch becomes on-state and eachof the coil elements 106 a to 106 f can detect MR signals. The couplingeffect between “the transmission RF coil 28 which transmits MR signalsto the object P” and “the coil elements 106 a to 106 f whichrespectively detect MR signals from the object P” is prevented by theabove on/off switching of the coil elements 106 a to 106 f.

Thirdly, in the pathway between the antennas 306 b and 206 b, a digitalreference signal is transmitted from the reference signal transmittingunit 318 of the control side radio communication device 300 to thereference signal receiving unit 218 of the coil side radio communicationdevice 200 at the start of a scan.

More specifically, the reference signal is a signal that synchronizes“the coil side radio communication device 200A as a transmission side ofMR signals” with “a basic frequency of system on the basis of the fixedfrequency generation unit 406”. The reference signal transmitting unit318 generates the reference signal by performing processing such asmodulation, frequency conversion, amplification and filtering on thecriteria clock signal inputted from the fixed frequency generation unit406.

As an example in the first embodiment, the reference signal receivingunit 218 includes a crystal controlled oscillator that can generate acriteria clock signal of a constant frequency and so on, so that thereference signal receiving unit 218 can generate the criteria clocksignal whose frequency is constant.

That is, the reference signal receiving unit 218 receives the referencesignal only at a start time of a scan, and starts generation of thereference signal in accordance with the timing of initial rise andfalling in the received reference signal. Note that, the later-described“trigger signal (A/D conversion start signal)” is superimposed on thereference signal received by the reference signal receiving unit 218 ata start time of a scan.

The reference signal receiving unit 218 continuously inputs thegenerated reference signal into each of the A/D converters 140 a to 140f during implementation term of a scan. Thereby, the MR signals detectedby the coil elements (106 a to 106 f) are normally subjected to A/Dconversion and then backed up by the memory elements 160 a to 160 f,even if a communication failure occurs between the coil side radiocommunication device 200A and the control side radio communicationdevices 300.

However, the reference signal may not be generated inside the referencesignal receiving unit 218. The reference signal may be continuouslywirelessly transmitted from the reference signal transmitting unit 318to the reference signal receiving unit 218 in the pathway between theantenna 306 b and the antenna 206 b.

The fixed frequency generation unit 406 generates the criteria clocksignal whose frequency is constant. The fixed frequency generation unit406 includes a crystal controlled oscillator with high degree ofstability and so on, in order to generate the criteria clock signal.

The fixed frequency generation unit 406 inputs the criteria clock signalto the reference signal transmitting unit 318 and the variable frequencygeneration unit 408. In addition, the fixed frequency generation unit406 inputs the criteria clock signal to respective components performingclock synchronization inside the MRI apparatus 20A such as the imagereconstruction unit 56 and the pulse waveform generation unit 404.

The variable frequency generation unit 408 includes PLL (Phase-LockedLoop), DDS (Direct Digital Synthesizer), and a mixer. The variablefrequency generation unit 408 operates on the basis of the abovecriteria clock signal. The variable frequency generation unit 408generates a local signal (clock signal) of variable frequency thataccords with a setting value inputted from the system control unit 52 asa center frequency of an RF pulse.

In order to achieve this, the system control unit 52 inputs a defaultvalue of the center frequency of the RF pulses to the variable frequencygeneration unit 408 before a prescan. In addition, the system controlunit 52 inputs a corrected value of the center frequency of the RFpulses to the variable frequency generation unit 408 after the prescan.

The variable frequency generation unit 408 inputs the above local signalof variable frequency to the frequency downconversion unit 410 and thefrequency upconversion unit 402.

In addition, “a trigger signal (A/D conversion start signal) thatdetermines timing of sampling in the A/D converters 140 a to 140 f ofthe cover member 104” is inputted from the system control unit 52 to thereference signal transmitting unit 318. The above sampling means, forexample, to extract intensity of an analog signal at regular timeintervals so as to enable digital record.

As an example here, the reference signal transmitting unit 318wirelessly transmits both the reference signal and the trigger signal tothe reference signal receiving unit 218 only at a start timing of ascan, by superimposing trigger signal on the reference signal.

Fourthly, in the pathway between the antennas 206 a and 306 a, digitizedMR signals are wirelessly transmitted from the data transmitting unit216 of the coil side radio communication device 200A to the datareceiving unit 316 of the control side radio communication device 300via an induced electric field.

More specifically, the analogue MR signals detected by each coil element(at least one of 106 a to 106 f) selected for detection are respectivelyamplified by the corresponding preamplifier (one of PMPa to PMPf), theninputted to the corresponding A/D converter (one of 140 a to 140 f), andthen converted into digital signals. At this time, the reference signaland trigger signal are inputted to each of the A/D converters 140 a to140 f from the reference signal receiving unit 218. Thus, each of theA/D converters 140 a to 140 f starts sampling and quantization on thebasis of the reference signal (sampling clock signal) in synchronizationwith the timing when the trigger signal is transmitted.

Each of the A/D converters 140 a to 140 f inputs the digitized MRsignals to the corresponding memory element (one of 160 a to 160 f) andthe P/S converter 144. That is, the A/D converter 140 a inputs the MRsignals which are detected by the coil element 106 a, amplified by thepreamplifier PMPa and digitized. Similarly, the A/D converter 140 binputs the MR signals which are detected by the coil element 106 b,amplified by the preamplifier PMPb and digitized. The same applies toeach of the A/D converters 140 c to 140 f.

However, if at least one of coil elements 106 a to 106 f is(are) notselected for detection, the preamplifier(s) (PMPa to PMPf) and the A/Dconverter(s) (140 a to 140 f) corresponding to the unselected coilelement(s) do not operate as an example in this embodiment.

The P/S converter 144 converts the inputted single or plural MRsignal(s) from parallel signals into a serial signal for radiotransmission, and inputs the serial signal to the data transmitting unit216 of the coil side radio communication device 200A via the cable 102.This is because the number of antenna for transmitting MR signals isonly one (the antenna 206 a) in the example of the first embodiment.

However, the present embodiment is not limited to the aspect oftransmitting MR signals as a serial signal. For example, MR signals maybe wirelessly transmitted as parallel signals by increasing the numberof antennas for transmitting and receiving MR signals.

The data transmitting unit 216 generates MR signals for radiotransmission (which are serial signals and digital signals) byperforming processing such as error correction encoding, interleave,modulation, frequency conversion, amplification, and filtering on theinputted serial MR signals. The data transmitting unit 216 wirelesslytransmits the MR signals for radio transmission from the antenna 206 ato the antenna 306 a.

The data receiving unit 316 performs processing such as amplification,frequency conversion, demodulation, deinterleave and error correctiondecoding on the serial MR signals received by the antenna 306 a.Thereby, the data receiving unit 316 extracts the original digitized MRsignals from the MR signals for radio transmission, and inputs theextracted MR signals to the frequency downconversion unit 410 of the RFreceiver 48.

The frequency downconversion unit 410 multiplies the MR signals inputtedfrom the data receiving unit 316 by the local signal inputted from thevariable frequency generation unit 408, and makes an arbitrary signalband get through by filtering. Thereby, the frequency downconversionunit 410 performs frequency conversion (downconversion) on the MRsignals, and inputs the MR signals whose frequency is lowered to thejudging unit 412.

The judging unit 412 generates the raw data of the MR signals byperforming predetermined signal processing on the above “MR signalswhose frequency is lowered”, and judges existence or non-existence of atransmission error on the basis of the raw data of the MR signals. Thejudging unit 412 specifies which part of the data corresponds to thetransmission error (lack of data and so on), when it judges that atransmission error exists. As to the method of judging whether or not atransmission error exists and the method of specifying the part of datacorresponding to a transmission error will be explained later with FIG.5.

The judging unit 412 inputs the raw data of the MR signals to the imagereconstruction unit 56. The image reconstruction unit 56 converts theraw data of the MR signals into k-space data and stores the k-space dataas described earlier.

Note that, though the RF receiver 48 and the control side radiocommunication device 300 are explained as mutually separate componentsin the above configuration, this is only an example. For example, the RFreceiver 48 may be a part of the control side radio communication device300.

In addition, the data receiving unit 316 may perform “the judgment as towhether or not a transmission error exists” and “the identification ofthe part of data corresponding to a transmission error”, instead of thejudging unit 412 in the RF receiver 48, for example. Alternatively, “thejudgment as to whether or not a transmission error exists” and “theidentification of the part of data corresponding to a transmissionerror” may be performed in the image reconstruction unit 56.

The foregoing is an explanation of the four radio communicationpathways.

In FIG. 4, the system control unit 52 determines the imaging conditionssuch as a repetition time (RF pulse cycle), a type of RF pulses, thecenter frequency of the RF pulses and a band width of the RF pulses in apulse sequence, on the basis of the imaging conditions inputted by auser via the input device 62. The system control unit 52 inputs theimaging conditions determined in the above manner to the pulse waveformgeneration unit 404.

The pulse waveform generation unit 404 generates a pulse waveform signalof baseband by using the criteria clock signal inputted from the fixedfrequency generation unit 406, depending on the imaging conditionsinputted from the system control unit 52 in the above manner. The pulsewaveform generation unit 404 inputs the pulse waveform signal ofbaseband to the frequency upconversion unit 402.

The frequency upconversion unit 402 multiplies the pulse waveform signalof baseband by the local signal inputted from the variable frequencygeneration unit 408, then makes an arbitrary signal band pass byfiltering, and thereby performs frequency conversion (upconversion). Thefrequency upconversion unit 402 inputs the pulse waveform signal ofbaseband whose frequency is raised to the RF transmitter 46. The RFtransmitter 46 generates the RF pulses on the basis of the inputtedpulse waveform signal.

FIG. 5 is an explanatory diagram showing the data type of MR signalsstored in the memory elements 160 a to 160 f. In FIG. 5, the phaseencode step number and the frequency encode step number are 256*256, butthis is only an example. Each step number may be another number asidefrom 256. In FIG. 5, TR is a repetition time, Ts in the horizontaldirection is a sampling time, and the longitudinal direction is thephase encode step.

In this case, for example, the phase encode is varied 256 times so as toacquire the MR signals of 256 lines for one image. More specifically,one line of the analogue MR signal detected by the coil element (106 ato 106 f) is amplified by the preamplifier (PMPa to PMPf). After this, asine wave or a cosine wave of the carrier frequency is subtracted fromthe amplified one line of the analogue MR signal and then this MR signalis digitized in the A/D converter (140 a to 140 f). That is, one line(corresponding to one phase encode step) of the MR signal is convertedinto data which have many digital values discretely existing in the timeaxis direction within a sampling time. Each digital number indicates,for example, intensity of the MR signal at the corresponding receipttime.

Such digitized MR signals are stored in the memory elements 160 a to 160f per line and inputted into the P/S converter 144 per line. The borderbetween one line and the next line of the MR signal can be discriminatedby the gate signal. That is, as an example in the present embodiment,each of the memory elements 160 a to 160 f backs up (stores) the MRsignals as the above digital data of frequency space.

The judging unit 412 judges (determines) whether a transmission error ispresent or not in the following manner, after generating the raw data ofthe MR signals by performing predetermined signal processing on thedigitized MR signals. For example, if data values corresponding to whitenoise are consecutive for a predetermined number, the judging unit 412judges that a transmission error exists. In addition, if the same datavalues are successively-placed for a predetermined number, the judgingunit 412 judges that a transmission error exists

The judging unit 412 specifies (identifies) “a part in which data valuescorresponding to white noise are consecutive for a predetermined number”and “a part in which the same data values are successively-placed for apredetermined number” as faulty parts of transmission (an incompletedata part corresponding to a transmission error), for example.

In addition, the judging unit 412 specifies (identifies) “the line ofwhich phase encode step of the MR signals detected by which of the coilelements 106 a to 106 f corresponds to the transmission error”, forexample.

In this case, a transmission error is judged per one line of the MRsignals, and retransmission of the correct data corresponding to thefaulty part of transmission is performed per one line, for example.However, this is only an example. Existence or non-existence of atransmission error may be judged per MR signals of one image andretransmission of the correct data corresponding to the faulty part maybe performed per MR signals of one image. Alternatively, even if atransmission error is included only in one line, retransmission of thecorrect data of the MR signals may be performed per MR signals of aplurality of images.

As just described, though retransmitted data includes correct datacorresponding to the faulty part, the retransmitted data may furtherinclude correct data which have been already successfully transmitted.Thus, to be exact, the above “retransmission of the correct datacorresponding to the faulty part” means “to retransmit data thatincludes the correct data corresponding to the faulty part due to atransmission error”.

In addition, though the radio communication pathway of the MR signals isonly one between the antenna 206 a and the antenna 306 a in the firstembodiment, existence or non-existence of a transmission error andidentification of the faulty part of transmission are preferablyperformed per radio communication pathway in the case of a plurality ofradio communication pathways of the MR signals.

For example, consider a case where the coil side radio communicationdevice 200A of the RF coil device 100A for the chest part is closelyfixed to one control side radio communication device 300 and the coilside radio communication device 200A of the RF coil device 100 a for thelumber part is closely fixed to another control side radio communicationdevices 300. In this case, the judging unit 412 identifies which part ofdata corresponds to a transmission error per RF coil device (100A and100α) and per coil element therein.

Note that, the respective lines of the MR signals inputted to the P/Sconverter 144 are wirelessly transmitted as described above, thenarranged in the order of the phase encode step in the imagereconstruction unit 56 like in FIG. 5, and finally converted into matrixdata.

More specifically, (for example, representative or average) intensity ofthe MR signal is defined as a matrix value of each matrix element per“ΔTS obtained by evenly dividing ‘the sampling time Ts of each MR signalcorresponding to the horizontal direction in FIG. 5’ by 256”.

Thereby, matrix data consisting of 256 rows and 256 columns arerespectively generated for the real number part (corresponding to thesection from which the above cosine function is subtracted) and theimaginary number part (corresponding to the section from which the abovesine function is subtracted). The image reconstruction unit 56 storesthese two sets of matrix data as k-space data.

Here, as to backup of the MR signals by each of the memory elements 160a to 160 f, “the judgment as to whether a scan is currently beingperformed or not” and “the judgment of a scan start timing” areimportant. In the following, some examples of the judgment methods willbe explained with FIG. 6 to FIG. 8. The judgment as to “whether a scanis currently being performed or not” can be achieved (determined) bychecking “whether an excitation RF pulse is transmitted or not”.

FIG. 6 is a schematic circuit diagram showing an example of judgingwhether or not it is in execution of a scan in the case of the activetrap circuit 170. Inside the cover member 104 of the RF coil device100A, an active trap circuit 170 is disposed between the selectioncontrol unit 108 and the coil elements 106 a.

The active trap circuit 170 includes a capacitor CA, a PIN diode D1 anda coil L3, and these elements are wired to the coil element 106 a asdescribed in FIG. 6.

The capacity of the capacitor CA, the inductance of the coil L3 and theresistance value of the PIN diode D1 in the forward direction areselected in such a manner that the resonance frequency of the loopcircuit circulating the capacitor CA, the PIN diode D1 and the coil L3becomes the Larmor frequency. In this case, the selection control unit108 can judge “whether a scan is currently being performed or not” onthe basis of the gate signal.

More specifically, if the coil element 106 a is selected for detection,the selection control unit 108 applies the turn-on voltage to the PINdiode D1 in the forward direction while the gate signal inputted fromthe gate signal receiving unit 224 is on-level. Therefore, during theon-level span of the gate signal, the PIN diode D1 becomes the on-state(conduction state).

In addition, during the on-level span of the gate signal, the loopcircuit circulating the capacitor CA, the PIN diode D1 and the coil L3resonates at the Larmor frequency and becomes high impedance state,because excitation RF pulses of the Larmor frequency are transmitted tothe object P. Thereby, the coil elements 106 a cannot detect an MRsignal because its electric current loop is blocked at the part of thecapacitor CA.

Thus, when an on-span is included in the gate signal inputted from thegate signal receiving unit 224, the selection control unit 108 judges“that a scan is currently performed until a predetermined time spanelapses starting from the on-span of the gate signal”. The abovepredetermined time span is, for example, a period needed for acquisitionof the MR signals and can be preliminarily determined on the basis ofthe imaging conditions such as a repetition time.

Note that, if the coil element 106 a is not selected for detection, theselection control unit 108 continues to apply the turn-on voltage to thePIN diode D1 in the forward direction. Thereby, the coil element 106 acannot detect MR signals and accordingly the coupling effect between thecoil element 106 a and other coil elements (106 b to 106 f) selected fordetection is prevented.

FIG. 7 is a schematic circuit diagram showing an example of judgingwhether or not it is in execution of a scan in the case of the passivetrap circuit 172. The passive trap circuit 172 includes a coil L4, acapacitor CB and “diodes D2 and D3 parallely-connected as a cross diodeCR”, and these circuit elements are wired to the coil element 106 a asshown in FIG. 7.

The capacity of the capacitor CB, the inductance of the coil L4 and theresistance values of the diodes D2 and D3 in the forward direction areselected in such a manner that the resonance frequency of the loopcircuit circulating the coil L4, the capacitor CB and the cross diode CRbecomes the Larmor frequency. The current detector 174 detects theelectric current value flowing the cross diode CR, and inputs thedetected value to the selection control unit 108.

In the following, the operation of the passive trap circuit 172 will beexplained.

When an excitation RF pulse of the Larmor frequency is transmitted tothe object P, an electric current momentarily flows the cross diode CRbecause the energy of an excitation RF pulse is large. Thereby, “theloop circuit of the coil L4, the capacitor CB and the cross diode CR”resonates and becomes a high impedance state. Therefore, the coilelements 106 a cannot detect an MR signal because its electric currentloop is blocked at the part of the capacitor CB.

Here, because the energy of the MR signals emitted from the object P dueto nuclear magnetic resonance is far weaker than the energy of anexcitation RF pulse, “an electric current which is large enough to applyturn-on voltage to each of the diodes D2 and D3” does not flow. Thus,during a span in which an excitation RF pulse is not transmitted, thepassive trap circuit 172 becomes on-state (conduction state to aradiofrequency current via the part of the capacitor CB). That is,during the span in which an excitation RF pulse is not transmitted, thecoil element 106 a can detect an MR signal because its electric currentloop is not blocked.

In addition, the acquisition of the MR signals is performed inaccordance with the imaging conditions such as a repetition time for acertain period of time after transmission of an excitation RF pulse.Thus, the selection control unit 108 obtains the electric current valueflowing the cross diode CR from the current detector 174 and judges“whether a scan is currently being performed or not” on the basis of theobtained electric current value.

That is, if the selection control unit 108 detects that an electriccurrent equal to or larger than a predetermined value is flowing thecross diode CR, the selection control unit 108 judges “that a scan iscurrently performed until a predetermined time span elapses startingfrom this detection timing”.

During a span in which an excitation RF pulse is transmitted, it ispreferable to protect the coil element 106 a by blocking the loop in theabove manner, and a trap circuit (170, 172) of FIG. 6 and/or FIG. 7 isincluded in the present embodiment. Although the part of the coilelement 106 a is explained in FIG. 6 and FIG. 7, the structure of thetrap circuits of other coil elements 106 b to 106 f is the same as FIG.6 or FIG. 7.

Note that, in the case of the passive trap circuit 172, the selectioncontrol unit 108 may judge “whether a scan is currently being performedor not” on the basis of the applied voltage value of the cross diode CR,instead of the electric current value of the cross diode CR. In thiscase, a voltage detector is disposed instead of the current detector174.

In the case of the above passive trap circuit 172, the coil elements 106a to 106 f detect the MR signals regardless of whether they are selectedfor detection or not. In the case of the passive trap circuit 172, “onlythe MR signals detected by the coil elements (106 a to 106 f) selectedfor detection out of the coil elements 106 a to 106 f” are subjected toA/D conversion, stored and wirelessly transmitted as described earlier.

In the case of the passive trap circuit 172, though it has an advantagein that the control of switching between on-state and off-state is notnecessary, the coupling effect between each of the coil elements 106 ato 106 f is not prevented like the active trap circuit 170 during thedetection span of the MR signals. Thus, in order to prevent the couplingeffect between each of the coil elements 106 a to 106 f, both of oneactive trap circuit 170 and one passive trap circuit 172 may be disposedfor each of the coil elements 106 a to 106 f. In this case, control ofthe passive trap circuit 172 is not necessary, and the same control maybe performed as to the active trap circuits 170 as described earlier.

FIG. 8 is an explanatory diagram showing an example of judging the starttiming of a scan on the basis of the transmission timing of anexcitation RF pulse. In FIG. 8, the horizontal axis indicates elapsedtime t from the start timing of a pulse sequence. The top part of FIG. 8indicates transmission timing of a waveform of an excitation RF pulse,and the bottom part of FIG. 8 indicates voltage values of the PIN diodeD1 of the active trap circuit 170.

As shown in FIG. 8, in the case of the active trap circuit 170, the PINdiode D1 becomes on-state and the voltage between both ends of the PINdiode D1 becomes the turn-on voltage during a span in which anexcitation RF pulse is transmitted (during the on-span of the gatesignal). Thus, if an off-span of the gate signal continues for “thefirst predetermined time span” and then the gate signal switches toon-level, the selection control unit 108 can judge that “the timing atwhich the gate signal is switched to on-level” is the start timing ofthe next scan. The above “first predetermined time span (see FIG. 8)”may be determined by the selection control unit 108 in accordance withthe imaging conditions.

The storage control unit 152 acquires the start timing of the next scanfrom the selection control unit 108 on a real-time basis, and may erasedata stored in the memory elements 160 a to 160 f in synchronizationwith the start timing of the next scan. This is because not acquisitionof the MR signals but a prescan for determining reception gain areperformed in the beginning of a scan in general. That is, data erasureis completed before digitizing and storing of the MR signals for imagegeneration of the next scan, even if the data erasure is startedimmediately after the start timing of the next scan.

On the other hand, if the passive trap circuit 172 is used for each ofthe coil elements 106 a to 106 f as a trap circuit, the selectioncontrol unit 108 judges the start timing of a scan as follows. Morespecifically, the selection control unit 108 makes the current detector174 detect the electric current value flowing the cross diode CR on asteady basis at regular time intervals.

If an electric current does not flow the cross diode CR for a time spanequal to or longer than the second predetermined time span, theselection control unit 108 judges “the timing at which an electriccurrent starts to flow the cross diode CR after this time span” as thestart timing of the next scan. The above “second predetermined time spancorresponds to “OFF PERIOD” in FIG. 8 and may be determined by theselection control unit 108 in accordance with the imaging conditions,for example.

If the start timing of a scan can be judged in the above manner, theselection control unit 108 can judge the finish time of a scan on thebasis of the start timing of a scan and the imaging conditions such as arepetition time and slice number.

Next, an example of methods for collecting data manually in the case ofa transmission error of data of the MR signals will be explained. As anexample in the MRI apparatus 20A of the first embodiment, if atransmission error of the MR signals occurs, the data stored in thememory elements (160 a to 160 f) are used so that the correct datacorresponding to a faulty part due to a transmission error areautomatically retransmitted after completion of the main scan.

The judging unit 412 judges whether a transmission error is present inthe retransmitted data or not. When the retransmission is not normallyperformed, the judging unit 412 identifies which part of datacorresponds to the transmission error as well as this part is originallydetected by which of the coil elements (106 a to 106 f), in theaforementioned manner. Then, the judging unit 412 inputs the identifiedresults to the system control unit 52. The system control unit 52 makesthe display device 64 display the memory element (at least one of 160 ato 160 f) corresponding to the coil element (at least one of 106 a to106 f) whose detection data are judged as the incompletely transmitteddata part.

FIG. 9 is a schematic diagram showing an example of a guide display inmethods of collecting data manually. The system control unit 52 makesthe display device 64 display the information which identifies the coilelement (at least one of 106 a to 106 f) to be taken out. In the displayexample of FIG. 9, a transmission error is present in at least a part ofdata of the MR signals detected by the coil elements 106 b and “a guidedisplay prompting a user to take out the memory element 160 bcorresponding to the coil elements 106 b and connect it to theafter-described data collecting unit 600” is displayed.

Although each of the memory elements 160 a to 160 f is detachable asdescribed earlier, it is preferable to make them visually mutuallydistinguishable by adding identification numbers on the surfaces of therespective memory elements 160 a to 160 f, for example.

When a plurality of the memory elements are included in the RF coildevice 100A, it is preferable to display the information whichidentifies the coil element (at least one of 106 a to 106 f) to be takenout as described earlier.

On the other hand, when only one memory element included in the RF coildevice 100A backs up the data detected by all of the coil elements 106 ato 106 f, a guide display is performed so as to prompt a user to takeout the memory element and connect it to the data collecting unit 600.

FIG. 10 is a schematic oblique drawing showing an example of arrangementof the data collecting unit 600. In the example of FIG. 10, though thedata collecting units 600 are emplaced at the entrance of the gantry 21of the imaging room for one and at the bed 32 for one respectively, thenumber of the data collecting units 600 may be one, three, or more thanthree. In addition, the arrangement of the data collecting units 600 isnot limited to the aspect shown in FIG. 10. For example, the datacollecting unit 600 may be emplaced in the control room.

Each of the data collecting units 600 is connected to the RF receiver 48by internal hard wiring, and includes the same type of connection portas the memory elements 160 a to 160 f.

Information which identifies the incomplete data part corresponding to atransmission error is inputted to each of the data collecting unit 600from the system control unit 52 (or the judging unit 412). When thememory element (at least one of 160 a to 160 f) is connected to the datacollecting unit(s) 600, each of the data collecting unit 600 obtains(reads in) the correct data corresponding to the incomplete data partfrom the connected memory element (at least one of 160 a to 160 f) onthe basis of the inputted information, and inputs the obtained data tothe RF receiver 48.

The correct data (corresponding to the faulty part due to a transmissionerror) obtained in the above manner are subjected to frequencydownconversion in the frequency downconversion unit 410 andpredetermined signal processing in the judging unit 412, and theninputted to the image reconstruction unit 56. The image reconstructionunit 56 compensates the incomplete data part corresponding to atransmission error, generates (corrects) k-space data on the basis ofthe compensated raw data of the MR signals, and stores the k-space data.Note that, regardless of which of the data collecting units 600 thememory element (at least one of 160 a to 160 f) is connected to, correctdata of the MR signals are collected in the same manner.

In addition, in order to prevent a transmission error, the systemcontrol unit 52 makes each component of the MRI apparatus 20A performacquisition of the identification information from the RF coil device100A and thereby checks whether the connection between the coil sideradio communication device 200A and the control side radio communicationdevices 300 is normal or not on a steady basis. The system control unit52 outputs a warning command indicating that the connection statusbetween the coil side radio communication device 200A and the controlside radio communication devices 300 is changed to abnormal status, whenthe system control unit 52 fails to normally (successfully) acquire theidentification information from the RF coil device 100A.

FIG. 11 is a schematic diagram showing an example of the warningdisplay, when the RF coil device 100α for the lumber part is used inaddition to the RF coil device 100A for the chest part and the radiocommunication status is not normal.

As an example in FIG. 11, the radio communication between the coil sideradio communication device 200A of the RF coil device 100A for the chestpart and one control side radio communication device 300 is normal, butthe radio communication between the coil side radio communication deviceof the RF coil device 100 a for the lumber part and another control sideradio communication device 300 is not normal.

Thus, the system control unit 52 inputs the warning command to thedisplay device 64, and makes the display device 64 display informationon where the radio communication is not normally performed (i.e. radiocommunication between which of the RF coil devices and which of thecontrol side radio communication devices 300 is not normal). Thisinformation is indicated by textual information at the bottom of theviewing surface with the arrangement diagram of the control side radiocommunication devices 300 in the table 34.

That is, the display device 64 functions as a notification unitnotifying that radio communication is not normal, when the radiocommunication is not normal. Note that, notification of abnormallyperformed radio communication is not limited to display, but it may beperformed, for example, by a warning sound. Alternatively, thenotification of abnormally performed radio communication may beperformed by emission of light such as blinking in red by arranging alight-emitting diode to an appropriate position.

FIG. 12 is a flowchart illustrating an example of flow of imagingoperation performed by the MRI apparatus 20A of the first embodiment. Inthe following, in accordance with the step numbers in the flowchartshown in FIG. 12, an operation of the MRI apparatus 20A will bedescribed by referring to the aforementioned FIG. 1 to FIG. 11 asrequired.

Note that, although a case of using the above RF coil device 100A willbe explained as an example here, the same effects as the firstembodiment can be obtained by disposing components similar to the coilside radio communication device 200A in other cases where other RF coildevices are used.

[Step S1] Under the state in which the table 34 is outside the gantry21, the RF coil device 100A is set on the object P on the table 34, andthe coil side radio communication device 200A is detachably closelyfixed to the nearest control side radio communication device 300 (seeFIG. 2 and FIG. 3).

If the coil side radio communication device 200A and the control sideradio communication device 300 fall within the range capable of mutualcommunication by the above short-distance fixation, the aforementionedelectric power supply and communication are started between both sides.

More specifically, the ID transmitting unit 222 wirelessly transmits theidentification information of the RF coil device 100A to the IDreceiving unit 322 by operating on the basis of electric powerwirelessly transmitted from the ID receiving unit 322 (see FIG. 4).

Here, the antenna 306 c of each the control side radio communicationdevice 300 outputs electromagnetic waves at regular time intervalsconstantly while the table 34 is not inserted into the gantry 21.Therefore, when the coil side radio communication device 200A is fixedwithin the range capable of radio communication, wireless transmissionof the identification information is immediately started.

The system control unit 52 acquires this identification information, andrecognizes that the RF coil device 100A is currently connected. Thereby,the system control unit 52 gives (outputs) a permission of furthercommunication between the coil side radio communication device 200A andthe control side radio communication device 300, and makes the powersupply unit 320 supply electric power to the power receiving unit 220.

Therefore, the power supply unit 320 and the power receiving unit 220start electric power supply to each component of the coil side radiocommunication device 200A and each component of the RF coil device 100A,via an induced magnetic field as described earlier.

After this, the table driving device 50 moves the table 34 into insideof the gantry 21 in accordance with control of the system control unit52.

In addition, the system control unit 52 makes each component of the MRIapparatus 20A continuously perform the processing of acquiring theidentification information of the RF coil device 100A from the coil sideradio communication device 200A at regular time interval until thecompletion of the pulse sequence. That is, the system control unit 52checks the connection status between the coil side radio communicationdevice 200A and the control side radio communication devices 300 on asteady basis. Then, the system control unit 52 outputs a caution commandand makes the display device 64 display the caution (warning), when theidentification information is not normally acquired (see FIG. 11).However, this processing is not performed during the implementation termof the processing of Step S11 and Step S12 in the case of taking out thememory element (at least one of 160 a to 160 f) with the table 34returned outside the gantry 21. Thus, there is a possibility that thewarning display is performed at an arbitrary timing from Step S1 to StepS10.

After this, the process proceeds to Step S2.

[Step S2] The system control unit 52 controls each component of the MRIapparatus 20A so as to become a standby state (ready state) for a pulsesequence. More specifically, the reference signal transmitting unit 318inputs the digital reference signal to the reference signal receivingunit 218 by the radio communication pathway between the antenna 306 band the antenna 206 b via, for example, an induced electric field, inaccordance with the communication permission outputted from the systemcontrol unit 52. Note that, a trigger signal for determining thesampling timing is superimposed on the transmitted reference signal.

As an example here, the reference signal receiving unit 218 receives thereference signal only at the beginning of a scan, and then startsgeneration of the reference signal so as to match the timing such asinitial rise and falling in the received reference signal. The referencesignal receiving unit 218 continuously inputs the generated referencesignal to each of the A/D converters (140 a to 140 f) until thecompletion of the main scan. Thereby, even if a transmission erroroccurs between the coil side radio communication device 200A and thecontrol side radio communication device 300, the MR signals detected bythe coil elements (106 a to 106 f) are amplified by the preamplifiers(PMPa to PMPf), then subjected to A/D conversion in the A/D converters(140 a to 140 f) and then stored in the memory elements (160 a to 160f).

After this, the process proceeds to Step S3.

[Step S3] After the start of inputting the reference signal from thereference signal receiving unit 218 to each of the A/D converters (140 ato 140 f), the selection control unit 108 of the RF coil device 100Ainputs a command of erasing data to the storage control unit 152. Thestorage control unit 152 starts erasure of all the data stored in allthe memory elements 160 a to 160 f in synchronization with the timing ofreceiving the command of erasing data. Thereby, an area of use iscompletely eliminated in every memory element (160 a to 160 f), and thememory elements 160 a to 160 f can back up data at a maximum.

After this, the process proceeds to Step S4.

[Step S4] The system control unit 52 sets some of the imaging conditionsof the main scan on the basis of “the imaging conditions inputted to theMRI apparatus 20A via the input device 62” and “information on thecurrently used RF coil device acquired in Step S1 (in this example,information indicating that the RF coil device 100A is used)”. Afterthis, the process proceeds to Step S5.

[Step S5] The system control unit 52 makes the MRI apparatus 20A performprescans by controlling each part of the MRI apparatus 20A. In theprescans, for example, a corrected value of the center frequency of theRF pulses is calculated, and a sensitivity distribution map of each ofthe coil elements 106 a to 106 f of the RF coil device 100A isgenerated.

After this, the process proceeds to Step S6.

[Step S6] The system control unit 52 sets the rest of the imagingconditions on the basis of the execution results of the prescans. Theimaging conditions include information on which of the coil elements (atleast one of 106 a to 106 f) are used for detection in the main scan.

Thus, the system control unit 52 inputs “the imaging conditionsnecessary for judging the star timing of a scan explained with FIG. 8”and “the information on the coil elements (at least one of 106 a to 106f) used for the main scan” into the selection control unit 108 of the RFcoil device 100A via any one of the radio communication pathways.

“The imaging conditions necessary for judging the star timing of a scan”and “the information on the coil element(s) used for detection” are, forexample, wirelessly transmitted from the gate signal transmitting unit324 to the gate signal receiving unit 224, and then inputted into theselection control unit 108 from the gate signal receiving unit 224.

After this, the process proceeds to Step S7.

[Step S7] The system control unit 52 makes the MRI apparatus 20A performthe main scan by controlling each component thereof.

More specifically, a static magnetic field is formed in the imagingspace by the static magnetic field magnet 22 excited by the staticmagnetic field power supply 40. In addition, the electric current issupplied from the shim coil power supply 42 to the shim coil 24, andthereby the static magnetic field formed in the imaging space isuniformed.

Note that, the aforementioned gate signal is continuously transmittedbetween the antennas 306 d and 206 d from the gate signal transmittingunit 324 to the gate signal receiving unit 224 during implementationterm of the main scan, if the switch of each of the coil elements 106 ato 106 f is the active trap circuit 170.

After this, when the system control unit 52 receives a command of startof imaging from the input device 62, the MR signals from the object Pare acquired (collected) by repeating the following processes of <1> to<4> in series.

<1> The system control unit 52 drives the gradient magnetic field powersupply 44, the RF transmitter 46 and the RF receiver 48 in accordancewith the pulse sequence, thereby gradient magnetic fields are formed inthe imaging region including the imaging part of the object P, and theRF pulses are transmitted from the transmission RF coil 28 to the objectP.

Note that, if the switch of each of the coil elements 106 a to 106 f isthe active trap circuit 170, the gate signal is set to, for example,on-level so as to set each of the coil elements 106 a to 106 f tooff-state only during the transmission period of the RF pulses. Thereby,the aforementioned coupling effect is prevented.

<2> If the switch of each of the coil elements 106 a to 106 f is theactive trap circuit 170, the gate signal is switched over to, forexample, off-level after transmission of the RF pulses.

Then, each of the coil elements (at least one of 106 a to 106 f)selected by the selection control unit 108 detects the MR signals causedby nuclear magnetic resonance inside the object P.

The detected analog MR signals are inputted from each of the coilelements (106 a to 106 f) to each of the corresponding preamplifiers(PMPa to PMPf), amplified by each of the corresponding preamplifiers(PMPa to PMPf), and then inputted to each of the corresponding A/Dconverters (140 a to 140 f), respectively.

Note that, the preamplifiers (PMPa to PMPf) and the A/D converters (140a to 140 f) respectively corresponding to the coil elements (106 a to106 f) which are not selected in the Step S4 do not operate.

<3> Each of the A/D converters (140 a to 140 f) corresponding to thecoil elements (106 a to 106 f) selected by the selection control unit108 starts sampling and quantization of the MR signals inputted from thecorresponding coil element, on the basis of the reference signalinputted from the reference signal receiving unit 218. Then, the A/Dconverters (140 a to 140 f) input the digitized MR signals to the P/Sconverter 144, respectively.

The P/S converter 144 converts the inputted plural MR signals into aserial signal, and inputs the serial signal to the data transmittingunit 216.

The data transmitting unit 216 generates MR signals for radiotransmission by performing predetermined processing on the serial signalof the MR signals, and wirelessly transmits the serial signal from theantenna 206 a to the antenna 306 a via induced electric fields.

<4> The data receiving unit 316 extracts the original digital MR signalsby performing predetermined processing on the serial signal for radiotransmission received by the antenna 306 a, and inputs the extracted MRsignals to the frequency downconversion unit 410.

The frequency downconversion unit 410 performs frequency downconversionon the inputted MR signals, and inputs “the MR signals whose frequencyis lowered” to the judging unit 412.

The judging unit 412 generates raw data of the MR signals by performingpredetermined processing on the inputted MR signals.

The judging unit 412 judges whether at least a part of the generated rawdata of the MR signals corresponds to a transmission error or not, inthe aforementioned manner.

When the judging unit 412 judges that at least a part of the generatedraw data corresponds to a transmission error, the judging unit 412identifies “a part in which data values corresponding to white noise areconsecutive for a predetermined number” and “a part in which the samedata values are successively-placed for a predetermined number” asincomplete data parts (faulty parts of transmission), for example.

In this example, the judging unit 412 identifies “the line of whichphase encode step of the MR signals detected by which of the coilelements 106 a to 106 f corresponds to the transmission error”.

As to “the raw data of the MR signals which do not include an incompletedata corresponding to a transmission error”, the judging unit 412directly inputs such data to the image reconstruction unit 56 (withoutchange). On the other hand, as to “the raw data of the MR signals whichare incomplete and corresponds to a transmission error”, such incompletedata are converted into substitution data by the judging unit 412 andthe substitution data are inputted from the judging unit 412 to theimage reconstruction unit 56, for example.

The substitution data are, for example, data whose values exclusivelyindicate the maximum luminance, and recognized as an incomplete datacorresponding to a transmission error by the image reconstruction unit56. The image reconstruction unit 56 converts the inputted raw data ofthe MR signals into k-space data and stores the k-space data.

The MR signals as the main scan are acquired by repeating the above <1>to <4> processes.

During implementation term of the main scan, as explained with FIG. 8,the start timing of the main scan is judged by the selection controlunit 108. Then, the storage control unit 152 starts erasing the datastored in the memory elements 160 a to 160 f in synchronization with thestart timing of the main scan, and the data erasure is completed beforethe start timing of storing data of the MR signals acquired in the mainscan.

In addition, during implementation term of the main scan, the selectioncontrol unit 108 continuously judges whether the main scan isconsecutively performed or not. As to this judging method, it isrespectively explained by using FIG. 6 and FIG. 7 in the case of theactive trap circuit 170 and in the case of the passive trap circuit 172.

During implementation term of the main scan, the selection control unit108 controls the storage control unit 152 so as to make the storagecontrol unit 152 back up data of the MR signals (which are beforewireless transmission). That is, the MR signals digitized by the A/Dconverter (at least one of 140 a to 140 f) corresponding to the selectedcoil element are stored in the memory element (at least one of 160 a to160 f) corresponding to this A/D converter. Thereby, data of all the MRsignals detected by the selected coil element(s) are backed up.

After completing the above main scan and backup of data of the MRsignals, the process proceeds to Step S8.

[Step S8] If a transmission error does not occur in the main scan inStep S7, the judging unit 412 inputs “the information indicating that atransmission error is not present” to the system control unit 52. Inthis case, the process proceeds to Step S13.

On the other hand, if a transmission error is present in the main scanin Step S7, the judging unit 412 inputs “the information indicating thata transmission error is present” and “the information identifying theincomplete data part corresponding to the transmission error” to thesystem control unit 52. In this case, the process proceeds to Step S9.

[Step S9] The system control unit 52 transmits “the informationidentifying the incomplete data part corresponding to the transmissionerror” to the selection control unit 108 of the RF coil device 100A viaany one of the radio communication pathways. For example, the systemcontrol unit 52 makes the gate signal transmitting unit 324 wirelesslytransmit “the information identifying the incomplete data partcorresponding to the transmission error” to the gate signal receivingunit 224. In this case, the gate signal receiving unit 224 inputs “theinformation identifying the incomplete data part corresponding to thetransmission error” to the selection control unit 108.

The selection control unit 108 controls the storage control unit 152 sothat “the correct data corresponding to the faulty part due to thetransmission error” are inputted from the memory element (at least oneof 160 a to 160 f) storing these correct data to the P/S converter 144.After this, the correct data corresponding to the transmission error arewirelessly retransmitted via an induced electric field in theaforementioned manner, subjected to frequency downconversion processing,and then inputted to the judging unit 412.

As described earlier, the retransmitted data may include not only “thecorrect data corresponding to the faulty part due to the transmissionerror” but also “previously normally transmitted data around the faultypart”.

After this, the process proceeds to Step S10.

[Step S10] The judging unit 412 generates the raw data of the MR signalsby performing a predetermined signal processing on the data of the MRsignals inputted in Step S9, and judges whether or not these dataincludes incomplete data part (whether or not these data correspond to atransmission error), in the aforementioned manner. The judging unit 412inputs the judgment result to the system control unit 52.

If the retransmitted data do not correspond to a transmission error, thejudging unit 412 inputs the raw data of the MR signals generated in thisStep S10 to the image reconstruction unit 56. Then, the imagereconstruction unit 56 substitutes the data inputted in this Step S10for the aforementioned substitution data so as to compensate theincomplete data corresponding to the transmission error. The imagereconstruction unit corrects the k-space data on the basis of thecompensated raw data of the MR signals in this manner, and stores thecorrected k-space data. After this, the process proceeds to Step S13.

On the other hand, if the retransmitted data correspond to atransmission error, the system control unit 52 (or the judging unit 412)inputs “the information identifying the incomplete data partcorresponding to the transmission error” to each of the data collectingunits 600. After this, the process proceeds to Step S11.

[Step S11] The system control unit 52 makes the display device 64perform the guide display of “the information on the memory element (atleast one of 160 a to 160 f) to be taken out” (see FIG. 9).

The above “memory element to be taken out” means the memory elementwhich stores the correct data which are unsuccessfully transmitted andcorrespond to a transmission error. In addition, the table drivingdevice 50 moves the table 34 to outside of the gantry 21 in order forthe memory element to be taken out in accordance with the control of thesystem control unit 52. In addition, the system control unit 52 makeseach component of the MRI apparatus 20A stop the acquisition processingof the identification information from the RF coil device 100A. Afterthis, the process proceeds to Step S12.

[Step S12] The memory element (at least one of 160 a to 160 f)identified by the guide display in Step S11 is manually detached fromthe RF coil device 100A by an operator, and the detached memory elementis connected to the data collecting unit 600. When the memory element(at least one of 160 a to 160 f) is connected thereto, the datacollecting unit 600 reads in the correct data corresponding to the partof a transmission error from the connected memory element and inputs(transfers) these data to the RF receiver 48. The data collecting unit600 erases all the data stored in the connected memory element (at leastone of 160 a to 160 f) after transferring the correct data correspondingto the transmission error.

The correct data corresponding to the transmission error are subjectedto frequency downconversion processing, then subjected to predeterminedsignal processing in the judging unit 412, and then inputted to theimage reconstruction unit 56. The image reconstruction unit 56substitutes the data inputted in this Step S12 for the aforementionedsubstitution data so as to compensate the incomplete data correspondingto the transmission error. The image reconstruction unit corrects thek-space data and stores the corrected k-space data in the way similar toStep S10. After this, the process proceeds to Step S13.

[Step S13] If there is not a next pulse sequence to be performed for thesame the object P, the system control unit 52 makes the MRI apparatus20A proceed to Step S14.

On the other hand, if there is a next pulse sequence to be performed forthe same the object P, the system control unit 52 makes the MRIapparatus 20A return to Step S2 by performing different processing forthe following two cases respectively.

Firstly, when the processing of Step S11 and Step S12 is not performed,the system control unit makes the MRI apparatus 20A return to Step S2under the state in which the processing of acquiring the identificationinformation from the RF coil device 100A is continuously performed.

Secondly, when the processing of Step S11 and Step S12 is performed, thesystem control unit 52 makes the display device 64 display “informationprompting an operator to reconnect ‘the memory element connected to thedata collecting unit 600’ to a predetermined position of the RF coildevice 100A”. After this, if the memory element is normally reconnectedin the data saving unit 150, the selection control unit 108 of the RFcoil device 100A makes the ID transmitting unit 222 restart transmissionof the identification information, and the system control unit 52restart the processing of acquiring the identification information fromthe RF coil device 100A. After this, the table driving device 50 movesthe table 34 to inside of the gantry 21 in accordance with control ofthe system control unit 52. After this, the process returns to Step S2.

[Step S14] The image reconstruction unit 56 reconstructs image data byperforming image reconstruction processing including Fouriertransformation on the k-space data. The image reconstruction unit 56stores the reconstructed image data in the image database 58.

After this, the image processing unit 60 obtains the image data from theimage database 58 and generates display image data by performingpredetermined image processing on the obtained image data. The imageprocessing unit 60 stores the display image data in the storage device66. Then, the system control unit 52 transmits the display image data tothe display device 64, and makes the display device 64 display imagesindicated by the display image data.

After completion of imaging, the table 34 is moved to outside of thegantry 21 and then the coil side radio communication device 200A isdetached from the control side radio communication device 300. When bothof them are moved beyond the range capable of radio communication, theradio communication and electric power supply between both sides areconcluded.

The foregoing is a description of the operation of the MRI apparatus 20Aaccording to the first embodiment. In the following, the effects of thefirst embodiment will be explained.

As just described in the first embodiment, the transmission side and thereceiving side are closely fixed to each other in time of radiocommunication, and the radio communication via an induced electric fieldis performed. Therefore, because output power of radio communication canbe more lowered than digital radio communication of conventionaltechnology, the MRI apparatus 20A of the present embodiment easilyaccommodates to legal regulations in various countries.

In addition to the mutually closely-situated transmission side andreceiving side, output power of radio communication can be lowered.Therefore, “the problem that the transmitted radio waves are reflectedoff surrounding areas and this degrades own data of radio communication”does not occur. Thus, digitized MR signals can be wirelessly transmittedsatisfactorily from the RF coil device 100A side to the control side ofthe MRI apparatus 20A (the RF receiver 48 side).

In addition, a plurality of the MR signals respectively detected by theplurality of the coil elements (106 a to 106 f) are converted into aserial signal and then wirelessly transmitted. Thus, the necessarynumber of an antenna for transmitting the MR signals (radiocommunication pathway) is only one pair, and frequency separation forpreventing interference is not necessary between each of the MR signals.

On the other hand, in the digital radio communication of conventionaltechnology, the receiving side is located far away from the transmissionside. Thus, in the digital radio communication of conventionaltechnology, frequency separation and time-multiplexed communication areperformed, because interference such as cross talk occurs if a pluralityof coil elements for receiving MR signals are simultaneously connected.In a short-distance radio communication like the present embodiment, itis not necessary to perform time-multiplexed communication.

In addition, the control side radio communication devices 300 arerespectively disposed to mutually separated positions, and it is enoughto fix the coil side radio communication device 200A to any one of thecontrol side radio communication devices 300. Thus, no matter which partof the object P an RF coil device is set on (i.e. no matter where the RFcoil device 100A is located on the table 34), the coil side radiocommunication device 200A and the control side radio communicationdevice 300 can be closely fixed to each other and the MR signals can bewirelessly transmitted satisfactorily.

In addition, because the electric power supply to the RF coil device100A, the transmission of the gate signal and the transmission of thetrigger signal are wirelessly performed, configuration of the MRIapparatus 20A can be simplified. As a result, cost of manufacturing theMRI apparatus 20A can be reduced.

Moreover, the MR signals detected by the coil elements (at least one of106 a to 106 f) selected for detection inside the RF coil device 100Aare respectively stored in the corresponding memory elements (one of 160a to 160 f). Then, if a transmission error is present in data of the MRsignals, the faulty data part corresponding to the transmission error isidentified by the judging unit 412 and the correct data corresponding tothe transmission error are automatically wirelessly retransmitted. Thus,according to the configuration of the MRI apparatus 20A, it is easy tocompensate a faulty data part of MR signals corresponding to atransmission error.

In addition, even if the faulty data part corresponding to thetransmission error is not compensated by the above wirelessretransmission of the correct data corresponding to the transmissionerror, the identification information of the memory element which storesthe correct data corresponding to the transmission error is displayed asa guide display. Thus, a faulty data part corresponding to atransmission error can be compensated only by detaching thecorresponding memory element from the RF coil device 100A and connectingit to the data collecting unit 600.

In addition, the system control unit 52 checks the connection status ofthe coil side radio communication device 200A on a steady basis.Thereby, the system control unit 52 makes the display device 64 performa warning display when the system control unit 52 fails to normallyacquire the identification information of the RF coil device 100A (seeexplanation of Step S1 and FIG. 11). Thus, the system control unit 52can prevent the MRI apparatus 20A from performing the main scan underthe state of abnormal connection (i.e. causing a transmission error ofdata of the MR signals).

In addition, because the memory elements 160 a to 160 f are disposedinside the electric field shield 156, they are not subject toelectromagnetic influence such as a static magnetic field and a gradientmagnetic field and thus they can infallibly back up data of the MRsignals.

In addition, the memory elements 160 a to 160 f store and erase dataelectrically. Therefore, reading and writing onto the memory elements160 a to 160 f do not influence magnetic resonance imaging.

In addition, the respective memory elements 160 a to 160 f areconfigured to be detachable, and the data collecting unit 600 formanually connecting the memory element (160 a to 160 f) and collectingdata backed up in the connected memory element is disposed. Thus, evenif a extraordinary situation such as power stoppage happens, the data ofthe MR signals detected and backed up before the extraordinary situationcan be infallibly collected.

In addition, the memory elements 160 a to 160 f respectivelycorresponding to the coil elements 106 a to 106 f are disposed, each ofthe memory elements (160 a to 160 f) stores data detected by thecorresponding coil element (one of 106 a to 106 f) only. Then, in timeof manual collection of data due to a transmission error, information onwhich of the memory elements (160 a to 160 f) should be taken out isdisplayed as a guide (Step S11 and FIG. 9). Thus, operation manualcollection of data is easy.

In addition, the selection control unit 108 judges the start timing ofthe main scan by the gate signal in the case of the active trap circuit170, and the selection control unit 108 judges the start timing of themain scan by an electric current value in the cross diode CR in the caseof the passive trap circuit 172. Thus, the selection control unit 108can accurately judge the start timing of the main scan. Insynchronization with the start timing of the main scan accurately judgedin this manner, all the data stored in the memory elements 160 a to 160f are erased in one lump. Thus, sufficient storage areas of data of theMR signals to be newly acquired can be kept at an appropriate timing.

In addition, the selection control unit 108 and the storage control unit152 make the memory elements 160 a to 160 f back up data of the MRsignals during implementation term of the main scan. Thus, the backupprocessing of data of the MR signals never prolongs a scan time.

In addition, the selection control unit 108 judges “whether the mainscan is consecutively performed or not”, on the basis of the gate signalin the case of the active trap circuit 170. Also, the selection controlunit 108 judges “whether the main scan is consecutively performed ornot”, on the basis of an electric current value in the cross diode CR inthe case of the passive trap circuit 172. Thus, because the selectioncontrol unit 108 can immediately judge the completion (timing) of themain scan at the finish time of the main scan, it is easy to determinethe completion timing of the backup processing of data of the MR signal.

According to the aforementioned embodiment, digitized MR signals can bewirelessly transmitted from an RF coil device to an MRI apparatussatisfactorily, in MRI. In addition, a transmission error of data of MRsignals caused by communication disturbance can be compensated.

The Second Embodiment

Next, the MRI apparatus 20B of the second embodiment will be explained.Note that, the MRI apparatuses 20B of the second embodiment differs onlyin “the method of collecting data of the MR signals which are backed up”from the first embodiment. Thus, only different points will beexplained.

FIG. 13 is a block diagram showing the general structure of the MRIapparatus 20B of the second embodiment. In the control room, the MRIapparatus 20B includes the system control unit 52, the input device 62,the display device 64, the storage device 66, the system bus 54, theimage reconstruction unit 56, the image database 58, the imageprocessing unit 60 and so on. Note that, the image database 58 and theimage processing unit 60 are not shown in FIG. 13 in order to avoidcomplication (see FIG. 1).

In addition, in the imaging room, the MRI apparatus 20B includes adata-collecting type charging unit 620, the gantry 21, the bed 32, thetable 34, the static magnetic field power supply 40, the shim coil powersupply 44, the gradient magnetic field power supply 44, the RFtransmitter 46, the RF receiver 48, the RF coil device 100B for thechest part and so on. Note that, the bed 32, the static magnetic fieldpower supply 40, the shim coil power supply 44, the gradient magneticfield power supply 44, the RF transmitter 46 are not shown in FIG. 13 inorder to avoid complication (see FIG. 1 and FIG. 4).

The data-collecting type charging unit 620 as one of the main featuresof the second embodiment is disposed as a charging stand inside the coilrack 610 in which various types of wearable RF coil devices such as anRF coil device for the chest part pr the lumber part are housed. Thedata-collecting type charging unit 620 is connected to the RF receiver48 by internal hard wiring, as an example here.

When the RF coil device 100B is put in the data-collecting type chargingunit 620, the data-collecting type charging unit 620 starts charging theRF coil device 100B, reads in the data of the MR signals backed up inthe memory elements of the RF coil device 100B, and transmits these datato the RF receiver 48.

More specifically, the RF coil device 100B includes a cover member 104′and the cable 102. The cover member 104′ is connected to the coil sideradio communication device 200A by the cable 102. The structure of thecover member 104′ is the same as the cover member 104 of the RF coildevice 100A of the first embodiment except the following two points.

Firstly, the cover member 104′ includes a connecting unit 190 which isinterdigitated with the data-collecting type charging unit 620.

Secondly, inside the cover member 104′, “hard wiring connecting thememory elements 160 a to 160 f in the data saving unit 150 to the RFreceiver 48 via the connecting unit 190 and the data-collecting typecharging unit 620” is disposed.

The data-collecting type charging unit 620 includes a connecting unit622 which is shaped in the form of interdigitating the connecting unit190 of the cover member 104′. The chassis of the data-collecting typecharging unit 620 includes a shape corresponding to the dent parts 321 ain FIG. 3 on the side opposite to the connecting unit 622, and therebyit is in the form of interdigitating the coil side radio communicationdevice 200A. In addition, the chassis of the data-collecting typecharging unit 620 includes a structure corresponding to the power supplyunit 320 in FIG. 4 on the side opposite to the connecting unit 622.

Therefore, when the cover member 104′ and the coil side radiocommunication device 200A are respectively interdigitated with thedata-collecting type charging unit 620, the data-collecting typecharging unit 620 starts to charge the rechargeable battery BA insidethe cover member 104′ through the cable 102, via an induced magneticfield. At the same time, the data-collecting type charging unit 620reads in the data of the MR signals backed up in the memory elements 160a to 160 f in the cover member 104′ and transmits these data to the RFreceiver 48.

During this period, the system control unit 52 may preliminarily inputthe information identifying the incomplete data part of the MR signalscorresponding to a transmission error via hard wiring (not shown), sothat the correct data corresponding to the incomplete data part aretransmitted to (the frequency downconversion unit 410 of) the RFreceiver 48. The judging unit 412 of the RF receiver 48 compensates theincomplete data part of the MR signals corresponding to a transmissionerror, performs the same processing as the first embodiment, and theninputs the (compensated) raw data of the MR signals to the imagereconstruction unit 56.

In addition, the data-collecting type charging unit 620 inputs a commandof data erasure to the storage control unit 152 of the cover member 104′via hard wiring (not shown) by way of the connecting unit 190 and 622,after completing transmission of data of the MR signals to the RFreceiver 48. The storage control unit 152 erases data stored in each ofthe memory elements 160 a to 160 f in synchronization with the receptiontiming of the command of data erasure.

FIG. 14 is a flowchart illustrating an example of flow of the imagingoperation performed by the MRI apparatus 20B of the second embodiment.In the following, according to the step numbers in the flowchart shownin FIG. 14, an operation of the MRI apparatus 20B will be described.

[Step S21 to S30] The processing contents of Step S21 to S30 are thesame as Step S1 to S10 in the first embodiment respectively. If anincomplete data part of the MR signals corresponding to a transmissionerror is not compensated in Step S30, the process proceeds to Step 31.If the incomplete data part is compensated, the process proceeds to Step32.

[Step S31] Information indicating the existence of an incomplete datapart of the MR signals caused by a transmission error is displayed as aguide display in the way similar to FIG. 9. At the same time, the systemcontrol unit 52 makes the display device 64 display a message to promptan operator to collect data. The message is, for example, “Please setthe RF coil device 100B and the coil side radio communication device200A to the data-collecting type charging unit 620, after completion ofthe pulse sequence”.

The “after completion of the pulse sequence” in the above message meansafter Step S32. This is because the process returns to Step S22 underthe state where the table 34 is still inside the gantry if the nextpulse sequence to be performed exists for the same object P.

Thus, as an example here, the system control unit 52 keeps the statewhere the processing of acquiring the identification information fromthe RF coil device 100B is consecutively performed. After this, theprocess proceeds to Step S32.

[Step S32] The processing of this Step S32 is similar to Step S13 of thefirst embodiment.

If the next pulse sequence for the same object P to be performed doesnot exist, the system control unit 52 brings forward the process to StepS33.

On the other hand, if the next pulse sequence to be performed exists forthe same object P, the system control unit 52 returns the process backto Step S22 under the state where the processing of acquiring theidentification information from the RF coil device 100B is (still)consecutively performed.

[Step S33] The image reconstruction processing and image display areperformed in the way similar to Step S14 of the first embodiment.However, the following processing is performed in front, if theprocessing of Step S31 has been performed.

More specifically, after completion of imaging, the table driving device50 moves the table 34 to outside of the gantry 21. Then, as explainedwith FIG. 13, the RF coil device 100B and the coil side radiocommunication device 200A are set to the data-collecting type chargingunit 620, and the correct data of the MR signals corresponding to theincomplete data part caused by a transmission error are collected.Thereby, after the incomplete data part caused by a transmission erroris compensated, the image reconstruction processing is started.

The foregoing is a description of an operation of the MRI apparatus 20Baccording to the second embodiment.

As just described, the same effects as the first embodiment can beobtained in the second embodiment. Moreover, in the second embodiment,“the processing of collecting the correct data corresponding to theincomplete data part caused by a transmission error” and “data erasureof the memory elements 160 a to 160 f” are performed in time of chargingthe RF coil device 100B after completion of the pulse sequence(s) forthe object P, if the incomplete data part caused by a transmission erroris not successfully compensated. Because data collection is performedwhile charging the RF coil device 100B, data collection never prolongs ascan time, similar to the first embodiment.

Supplementary Notes on Embodiments

In the following, supplementary notes on the aforementioned embodimentswill be explained.

[1] In the first embodiment and the second embodiment, an example inwhich the data saving unit 150 is disposed inside the cover member 104of the RF coil device 100A has been explained. However, embodiments ofthe present invention are not limited to such an aspect. The data savingunit 150 may be disposed inside the coil side radio communication device200A.

Alternatively, the data saving unit 150 may be disposed to the stagesubsequent to the P/S converter 144. In this case, the memory elementsinside the data saving unit 150 back up data of the MR signals convertedinto a serial signal. In this case, if a plurality of coil elements areselected for detection, the MR signals detected by these coil elementsmay be, for example, backed up in one memory element in one lump.

[2] In the first embodiment, an example in which the data stored in thememory elements 160 a to 160 f are instantaneously erased at the starttiming of each main scan has been explained. However, embodiments of thepresent invention are not limited to such an aspect. If the memorycapacity of each of the memory elements 160 a to 160 f is sufficientlylarge, for example, the data stored in the memory elements 160 a to 160f may be erased after completing all the pulse sequences for one patient(the same object P). Alternatively, the data stored in the memoryelements 160 a to 160 f may be erased at the timing of restarting theMRI apparatus 20A.

[3] If a plurality of RF coil devices for detecting MR signals are setto one object, these RF coil devices may be connected in parallel toeach other, and data of the MR signals detected by one of the RF coildevices may be doubly backed up in the respective memory elements ofboth RF coil devices.

FIG. 15 is a block diagram showing an example of connecting the RF coildevice 100γ for the lumber part and the RF coil device 100C for thechest part in parallel to each of the control side radio communicationdevices 300.

In this example, though only two coil elements are respectively arrangedin the RF coil device 100C for the chest part and the RF coil device100γ for the lumber part for the sake of avoiding complication, three ormore than three coil elements may be arranged in each of the RF coildevices 100C and 100γ

The RF coil device 100C for the chest part includes a data communicationdevice 200C, a cover member 104 c and a cable (not shown), and isconnected to the coil side radio communication device 200A via thecable. The coil side radio communication device 200A connected to the RFcoil device 100C for the chest part is closely fixed to one control sideradio communication device 300. The MR signals detected by the RF coildevice 100C for the chest part are wirelessly transmitted between thecoil side radio communication device 200A and the control side radiocommunication device 300 via an in an induced electric field asdescribed earlier.

The RF coil device 100γ for the lumber part includes a datacommunication device 200C′, a cover member 104γ, and a cable (notshown), and is connected to the coil side radio communication device200A via the cable. The coil side radio communication device 200Aconnected to the RF coil device 100γ for the lumber part is closelyfixed to another control side radio communication device 300 differentfrom that for the RF coil device 100C for the chest part. The MR signalsdetected by the RF coil device 100γ for the lumber part are wirelesslytransmitted between the coil side radio communication device 200A andthe control side radio communication device 300 via an induced electricfield as described earlier.

Inside the cover member 104 c of the RF coil device 100γ for the lumberpart, each of coil elements 106α, 106β are disposed for detecting the MRsignals from the lumber part. Although components such as therechargeable battery BA are disposed inside the cover member 104 c inthe way similar to the cover member 104 in FIG. 4, they are not shown inFIG. 15 in order to avoid complication.

The data communication devices 200C and 200C′ respectively includecomponents for the radio communication via an induced electric fieldsuch as induced electric field combined couplers. The chassis of thedata communication device 200C has a plurality of juts interdigitatedwith the data communication device 200C′. The chassis of the datacommunication device 200C′ has insertion holes interdigitated with theabove plurality of juts. Thereby, the data communication devices 200Cand 200C′ are fixed in close contact with each other.

Note that, antennas are disposed inside each of the chassis. Thus, evenif the chassis of each of the data communication devices 200C and 200C′is fixed in close contact with each other, each of their antennas nevercontacts another antenna, and there is no problem on the radiocommunication.

The data communication device 200C wirelessly transmits the MR signalsdetected by the RF coil device 100C for the chest part to the datacommunication device 200C′ via an induced electric field in the waysimilar to the first embodiment. That is, the MR signals detected by thecoil elements 106 a and 106 b of the RF coil device 100C for the chestpart are respectively amplified by the preamplifier PMPa and PMPa, thenrespectively subjected to A/D conversion in the A/D converter 140 a and140 b, then converted into a serial signal in the P/S converter 144, andthen wirelessly transmitted to the data communication device 200C′.

The data communication device 200C′ converts the received serial signalinto the original parallel signals (a plurality of digitized MR signalscorresponding to the respective coil elements 106 a and 106 b). Afterthis, the data communication device 200C′ inputs the MR signals detectedby the coil elements 106 a to the memory element 160 a, and inputs theMR signals detected by the coil elements 106 b to the memory element1608.

The storage control unit 152 of the RF coil device 100γ for the lumberpart stores “the MR signals wirelessly transmitted after being detectedby the coil elements 106 a” and “the MR signals detected by the coilelements 106α of the RF coil device 100γ for the lumber part amplifiedby the preamplifier PMPa, and digitized by the A/D converters 140α” inthe memory element 160α.

In addition, the storage control unit 152 of the RF coil device 100γ forthe lumber part stores “the MR signals wirelessly transmitted afterbeing detected by the coil elements 106 b” and “the MR signals detectedby the coil elements 106β of the RF coil device 100γ for the lumber partamplified by the preamplifier PMPβ and digitized by the A/D converters140γ” in the memory element 160β.

Similarly, the MR signals detected by the coil elements 106α and 106β ofthe RF coil device 100γ for the lumber part are respectively convertedinto a serial signal in the P/S converter 144, and then wirelesslytransmitted from the data communication device 200C′ to the datacommunication device 200C. The data communication device 200C convertsthe received serial signal into the parallel signals as describedearlier. The data communication device 200C inputs the MR signalsdetected by the coil elements 106α to the memory element 160 a, andinputs the MR signals detected by the coil elements 106β to the memoryelement 160 b.

The storage control unit 152 of the RF coil device 100C for the chestpart stores “the MR signals wirelessly transmitted after being detectedby the coil elements 106α” and “the MR signals detected by the coilelements 106 a digitized by the A/D converters 140 a” in the memoryelement 160 a.

In addition, the storage control unit 152 of the RF coil device 100C forthe chest part stores “the MR signals wirelessly transmitted after beingdetected by the coil elements 106β” and “the MR signals detected by thecoil elements 106 b and digitized by the A/D converters 140 b” in thememory element 160 b.

As just described, the MR signals respectively detected by the coilelements 106 a, 106 b, 106α and 106β of the RF coil device 100C for thechest part and the RF coil device 100γ for the lumber part are doublybacked up by the respective memory elements 160 a, 160 b, 160α and 160βinside the RF coil device 100C for the chest part and the RF coil device100γ for the lumber part. Thereby, the MRI apparatus 20B can makeabsolutely sure to protect data of the MR signals.

[4] If a plurality of RF coil devices for detecting MR signals are setto an object, these RF coil devices may be connected in series and onlythe coil side radio communication device on the side of one RF coildevice may be closely fixed to the control side radio communicationdevices 300.

FIG. 16 is a block diagram showing an example of mutually connecting theRF coil device 100A for the lumber part, the RF coil device 100D for thechest part, and one control side radio communication device 300 inseries.

The RF coil device 100D for the chest part includes a cover member 104d, the coil side radio communication device 200A and a cable (not shown)connecting these components each other.

As an example here, the structure of the cover member 104 d is the sameas the cover member 104 of the first embodiment, except including arechargeable battery BAT preliminarily charged before imaging instead ofthe rechargeable battery BA charged via an induced magnetic field.

The rechargeable battery BAT supplies electric power to each componentof the RF coil device 100D for the chest part via hard wiring (notshown).

The RF coil device 100Δ for the lumber part includes a datacommunication device 300Δ, a cover member 104Δ and a cable (not shown).The RF coil device 100D for the chest part is connected to another coilside radio communication device 200A by the cable. The structure of thecover member 104Δ is the same as the cover member 104γ explained withFIG. 15 except the following two points.

Firstly, the memory elements 160α and 160β do not store the MR signalsdetected by the RF coil device 100D for the chest part, but respectivelystore the digitized MR signals detected by the coil elements 106α and106β.

Secondly, a signal conflating unit 196 which conflates the following twoserial signals into one serial signal is disposed in the cover member104.

One of the two serial signals is a serial signal of the MR signals whichare detected by the coil elements 106 a and 106 b of the RF coil device100D for the chest part, digitized, and wirelessly transmitted from thecoil side radio communication device 200A to the data communicationdevice 300Δ as a serial signal.

The other of the two serial signals is a serial signal of the MR signalswhich are detected by the coil elements 106α and 106β of the RF coildevice 100Δ for the lumber part, digitized and converted into a serialsignal by the P/S converter 144.

That is, the signal conflating unit 196 inputs the serial signalincluding the MR signals detected by the four coil elements 106 a, 106b, 106α and 106β into the coil side radio communication device 200A.

The coil side radio communication device 200A on the side of the RF coildevice 100Δ for the lumber part is closely fixed to the control sideradio communication devices 300 on the table 34, and wirelesslytransmits the serial signal inputted from the signal conflating unit 196to the control side radio communication device 300 in the way similar tothe first embodiment.

The data communication device 300Δ is shaped in the form ofinterdigitating the coil side radio communication device 200A like thecontrol side radio communication device 300. The data communicationdevice 300Δ includes components for the radio communication via aninduced electric such as induced electric field combined couplers. Thedata communication device 300Δ receives “the serial signal including theMR signals detected by the coil elements 106 a and 106 b” from the coilside radio communication device 200A on the side of the RF coil device100D for the chest part, by way of the radio communication via aninduced electric field.

As just described, when a plurality of RF coil devices for detecting MRsignals are connected in series and only the coil side radiocommunication device on the side of one RF coil device is closely fixedto the control side radio communication device 300, the number of thecontrol side radio communication devices 300 to be used is only one. Inthis case, the channel number of the RF receiver 48 to be used can bereduced.

[5] The modified embodiments in which a plurality of RF coil device fordetecting MR signals are connected in series or in parallel describedwith FIG. 15 and FIG. 16 can be applied to cases of using RF coildevices for other parts such as the head and the shoulder. In addition,the number of the RF coil devices connected in series or in parallel isnot limited to two, but it may be three or more than three.

[6] While certain embodiments have been described, these embodimentshave been presented by way of example only, and are not intended tolimit the scope of the inventions. Indeed, the novel methods and systemsdescribed herein may be embodied in a variety of other forms;furthermore, various omissions, substitutions and changes in the form ofthe methods and systems described herein may be made without departingfrom the spirit of the inventions. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the inventions.

What is claimed is:
 1. A magnetic resonance imaging apparatuscomprising: an RF coil assembly that includes an analog to digitalconverter and digital storage configured to detect a nuclear magneticresonance (NMR) signal emitted from an object, digitize the NMR signaland store a digitized NMR signal in the digital storage; a radiofrequency (RF) transmitter that wirelessly transmits the digitized NMRsignal; an RF receiver that wirelessly receives the digitized NMR signalfrom the RF transmitter; an image reconstruction circuit thatreconstructs image data of the object based on the digitized NMR signalreceived by the RF receiver; and a system controller configured to judgewhether radio communication between the RF transmitter and the RFreceiver is normal or not, wherein the RF transmitter is configured towirelessly transmit identification information of the RF coil assemblyto the RF receiver; and the system controller is configured to judgewhether the radio communication between the RF transmitter and the RFreceiver is normal or not, based on the identification informationreceived by the RF receiver.
 2. The magnetic resonance imaging apparatusaccording to claim 1, wherein the system controller is configured toidentify an incomplete data part in data of the digitized NMR signal,when the system controller judges that the transmission error ispresent; and the RF transmitter is configured to wirelessly retransmitdata including correct data corresponding to the incomplete data part tothe RF receiver, when the system controller judges that the transmissionerror is present.
 3. The magnetic resonance imaging apparatus accordingto claim 1, further comprising a notification circuit configured tonotify that the radio communication is not normal, when the systemcontroller judges that the radio communication between the RFtransmitter and the RF receiver is not normal.
 4. The magnetic resonanceimaging apparatus according to claim 3, wherein the digital storageincludes an memory element in which data of the digitized NMR signal arestored and erased electrically or by laser.
 5. The magnetic resonanceimaging apparatus according to claim 4, wherein the digital storageincludes a semiconductor memory element in which data of the digitizedNMR signal are electrically stored, and an electric field shieldcovering the semiconductor memory element.
 6. The magnetic resonanceimaging apparatus according to claim 4, further comprising a datacollecting circuit configured to be connectable with the memory elementand read in data of the digitized NMR signal stored in the memoryelement; wherein the memory element is configured to be detachable fromthe digital storage and the collecting circuit.
 7. The magneticresonance imaging apparatus according to claim 1, wherein the RFtransmitter is configured to wirelessly transmit the digitized NMRsignal via an induced electric field; and the RF receiver is configuredto wirelessly receive the digitized NMR signal from the RF transmitter,via an induced electric field.
 8. The magnetic resonance imagingapparatus according to claim 7, wherein the digital storage isconfigured to store the digitized NMR signal as data in a frequencyspace.
 9. The magnetic resonance imaging apparatus according to claim 1,wherein the RF coil assembly includes a plurality of coil elementsrespectively configured to detect the NMR signal from the object, and aselection controller configured to select at least one of the pluralityof coil elements used for a scan which is an operation of acquiring NMRsignals by the magnetic resonance imaging apparatus; and the digitalstorage is configured to store, during implementation term of the scan,the NMR signal detected by a coil element selected by the selectioncontroller.
 10. The magnetic resonance imaging apparatus according toclaim 9, wherein the RF coil assembly includes a plurality of trapcircuits configured to respectively correspond to the plurality of coilelements and switch on/off of function of the plurality of coil elementsfor detecting the NMR signal, in accordance with control of theselection controller; and the selection controller is configured toacquire a gate signal stipulating switching timing of impedance of thetrap circuits, control the trap circuits based on the gate signal, andjudge whether a scan is currently performed or not, based on the gatesignal.
 11. The magnetic resonance imaging apparatus according to claim10, wherein the selection controller is configured to judge start timingof the scan based on the gate signal.
 12. The magnetic resonance imagingapparatus according to claim 11, wherein digital storage is configuredto start erasure of data of the digitized NMR signal stored therein, insynchronization with the start timing of the scan judged by theselection controller.
 13. The magnetic resonance imaging apparatusaccording to claim 9, wherein the RF coil assembly includes a pluralityof trap circuits configured to respectively correspond to the pluralityof coil elements and switch on/off of function of the plurality of coilelements for detecting the NMR signal; and the selection controller isconfigured to judge whether a scan is currently performed or not, basedon an electric current value or a voltage value in at least one of thetrap circuits.
 14. The magnetic resonance imaging apparatus according toclaim 13, wherein the selection controller is configured to judge starttiming of the scan based on an electric current value or a voltage valuein at least one of the trap circuits.
 15. The magnetic resonance imagingapparatus according to claim 9, wherein the digital storage includes aplurality of memory elements respectively corresponding to the pluralityof coil elements, and stores the digitized NMR signal in a memoryelement corresponding to a coil element selected by the selectioncontroller during implementation term of the scan.
 16. The magneticresonance imaging apparatus according to claim 1, further comprising: arechargeable battery configured to be embedded in the RF coil assemblyand supply electric power to the RF coil assembly; a second RF receiverconfigured to acquire the digitized NMR signal from the first-mentionedRF receiver, perform frequency conversion processing on the digitizedNMR signal, and input data of the digitized NMR signal after thefrequency conversion processing into the image reconstruction circuit;and a data-collecting charging unit configured to be detachable from theRF coil assembly, and charge the rechargeable battery as well astransmit data stored in the digital storage into the second RF receiverin a case of being connected to the RF coil assembly.
 17. The magneticresonance imaging apparatus according to claim 16, wherein thedata-collecting charging unit is configured to input a command of dataerasure to the digital storage, after completion of transmitting datastored in the digital storage; and the digital storage is configured toerase data stored therein in a case of receiving the command of dataerasure.
 18. The magnetic resonance imaging apparatus according to claim1, further comprising at least two of said RF coil assemblies, whereineach of the RF coil assemblies includes a communication circuitconfigured to transmit and receive the NMR signal via an inducedelectric field; the digital storage of one of the RF coil assembliesbeing configured to store the NMR signal detected by said one of the RFcoil assemblies, and the NMR signal received by the communicationcircuit of said one of the RF coil assemblies after being detected byanother of the RF coil assemblies; and the digital storage of saidanother of the RF coil assemblies is configured to store the NMR signaldetected by said another of the RF coil assemblies, and the NMR signalreceived by the communication device of said another of the RF coilassemblies after being detected by said one of the RF coil assemblies.19. The magnetic resonance imaging apparatus according to claim 1,further comprising at least two of said RF coil assemblies, wherein eachof the RF coil assemblies includes a communication circuit configured totransmit and receive the NMR signal via an induced electric field; thecommunication circuit of one of the RF coil assemblies being configuredto wirelessly transmit the NMR signal detected by said one of the RFcoil assemblies to the communication circuit of another of the RF coilassemblies; and the RF transmitter is configured to be connected withsaid another of the RF coil assemblies, and wirelessly transmit the NMRsignal detected by said another of the RF coil assemblies and the NMRsignal received by the communication circuit after being detected bysaid one of the RF coil assemblies.